IRS NOTICE REFERENCE CATALOG
All 448 IRS notices — factual reference
Category, governing IRC section, statutory response window, and what the IRS says to do for every notice in the catalog. Rule-based severity scores — the same severity read every time. General information only. Not legal or tax advice.
General information only. Not legal or tax advice.
This catalog covers 448 IRS notices and letters sourced from IRS.gov and the Taxpayer Advocate Service. Each entry shows the factual metadata from the IRS — what the notice is, the governing IRC section, and the statutory response window if one applies. Severity tiers are assigned by a rule-based scoring system — not by AI, not by guesswork.
For hand-written, practitioner-focused explainers on the 13 most common notices, see the curated notice library. For the first-hour workflow tool, try the free IRS Notice Checker.
Criminal Investigation
Criminal Investigation notices — get counsel first
Notices in this category relate to IRS Criminal Investigation. Do not contact the IRS, provide records, or make statements before consulting a tax attorney or criminal defense counsel. CPA privilege does not apply in criminal matters.
CP94
Understanding your CP94 notice — Tier 5 — Criminal Investigation · Escalation flag
Appeals and collection due process
CP177
Understanding Your CP177 Notice — Tier 4 — Escalation warranted · 30-day window · Escalation flag
CP242
Understanding your CP242 notice — Tier 4 — Escalation warranted · 30-day window · Escalation flag
CP297
Understanding Your CP297 Notice — Tier 4 — Escalation warranted · 30-day window · Escalation flag
CP297A
Understanding Your CP297A Notice — Tier 4 — Escalation warranted · 30-day window · Escalation flag
CP297C
Understanding Your CP297C Notice — Tier 4 — Escalation warranted · 30-day window · Escalation flag
CP298
Understanding your CP298 notice — Tier 4 — Escalation warranted · 30-day window · Escalation flag
CP400-AND-CP401
Understanding your CP400 and CP401 notice — Tier 2 — Action or response expected
CP77
Understanding your CP77 notice — Tier 4 — Escalation warranted · 30-day window · Escalation flag
CP90
Understanding your CP90 notice — Tier 4 — Escalation warranted · 30-day window · Escalation flag
CP90C
Understanding your CP90C notice — Tier 4 — Escalation warranted · 30-day window · Escalation flag
CP91
Understanding your CP91 notice — Tier 4 — Escalation warranted · Escalation flag
CP92
Understanding your CP92 notice — Tier 4 — Escalation warranted · 30-day window · Escalation flag
LP59
Understanding your LP59 notice — Tier 4 — Escalation warranted · 30-day window · Escalation flag
LP68
Understanding Your LP68 Notice — Tier 1 — Routine
LT11 / Letter 1058
Understanding your LT11 notice or letter 1058 — Tier 4 — Escalation warranted · 30-day window · Escalation flag
LT16
Understanding your LT16 notice — Tier 4 — Escalation warranted · Escalation flag
LT73
Understanding your LT73 notice — Tier 4 — Escalation warranted · Escalation flag
LT75
Understanding your LT75 notice — Tier 4 — Escalation warranted · Escalation flag
Letter 6468
Understanding Your Letter 6468 — Tier 2 — Action or response expected
Letter 6469
Understanding Your Letter 6469 — Tier 2 — Action or response expected
Letter 6470
Understanding Your Letter 6470 — Tier 2 — Action or response expected
Equivalent Hearing (Within 1 Year)
Equivalent Hearing (Within 1 Year) — Tier 4 — Escalation warranted · 30-day window · Escalation flag
Letter 11
Letter 11 — Tier 4 — Escalation warranted · 30-day window · Escalation flag
Letter 3171
Letter 3171 — Tier 4 — Escalation warranted · 30-day window · Escalation flag
Letter 3172
Letter 3172 — Tier 4 — Escalation warranted · 30-day window · Escalation flag
Letter 3177
Letter 3177 — Tier 4 — Escalation warranted · Escalation flag
Letter 3193
Letter 3193 — Tier 4 — Escalation warranted · 30-day window · Escalation flag
Letter 3210
Letter 3210 — Tier 4 — Escalation warranted · Escalation flag
Letter 3288
Letter 3288 — Tier 4 — Escalation warranted · Escalation flag
Letter 3846
Letter 3846 — Tier 4 — Escalation warranted · Escalation flag
Letter 3886
Letter 3886 — Tier 4 — Escalation warranted · Escalation flag
Letter 4380
Letter 4380 — Tier 4 — Escalation warranted · 30-day window · Escalation flag
Letter 4389
Letter 4389 — Tier 4 — Escalation warranted · 30-day window · Escalation flag
Letter 4390
Letter 4390 — Tier 4 — Escalation warranted · 30-day window · Escalation flag
Letter 4439
Letter 4439 — Tier 4 — Escalation warranted · Escalation flag
Letter 4440
Letter 4440 — Tier 4 — Escalation warranted · 180-day window · Escalation flag
Letter 4837
Letter 4837 — Tier 4 — Escalation warranted · Escalation flag
Letter 5157
Letter 5157 — Tier 3 — Time-sensitive response
Letter 965
Letter 965 — Tier 3 — Time-sensitive response
Letter 966
Letter 966 — Tier 3 — Time-sensitive response
Letter 970-C
Letter 970 — Tier 3 — Time-sensitive response
Letter 970-L
Letter 970 — Tier 3 — Time-sensitive response
Examination and audit
CP05A
Understanding your CP05A notice — Tier 2 — Action or response expected
CP06-CP06A
Understanding your CP06/CP06A notice — Tier 3 — Time-sensitive response · 30-day window
CP120
Understanding Your CP120 Notice — Tier 2 — Action or response expected
CP158
Understanding your CP158 notice — Tier 2 — Action or response expected
CP2005
Understanding your CP2005 notice — Tier 1 — Routine
CP28A
Understanding your CP28A notice — Tier 2 — Action or response expected
CP3219N
Understanding your CP3219N notice — Tier 4 — Escalation warranted · 90-day window · Escalation flag
CP590A
Understanding your CP590A notice — Tier 3 — Time-sensitive response · Escalation flag
CP591
Understanding your CP591 notice — Tier 2 — Action or response expected
CP593
Understanding your CP593 notice — Tier 2 — Action or response expected
CP75
Understanding your CP75 notice — Tier 3 — Time-sensitive response
CP75A
Understanding your CP75A notice — Tier 3 — Time-sensitive response
CP75D
Understanding your CP75D notice — Tier 3 — Time-sensitive response
LP61
Understanding your LP61 notice — Tier 2 — Action or response expected
Letter 3164
Understanding your letter 3164 — Tier 3 — Time-sensitive response
Letter 4087C
Understanding your letter 4087C — Tier 2 — Action or response expected · 30-day window
Letter 4800C
Understanding your letter 4800C — Tier 3 — Time-sensitive response · 30-day window
Letter 6255C
Understanding your letter 6255C — Tier 2 — Action or response expected
Letter 6612
Understanding your letter 6612 — Tier 3 — Time-sensitive response
Initial Contact Letter
Initial Contact Letter — Tier 3 — Time-sensitive response
Letter 2202-B
Letter 2202 B — Tier 3 — Time-sensitive response
Letter 3253
Letter 3253 – Taxpayer Appointment Confirmation — Tier 1 — Routine
Letter 3573
Letter 3573 – SBSE Office Exam Appointment Confirmation — Tier 1 — Routine
Letter 525
General 30-Day Letter — Tier 3 — Time-sensitive response · 30-day window
Letter 915
Examination Report Transmittal — Tier 3 — Time-sensitive response · 30-day window
Balance due and collection
CP101
Understanding Your CP101 Notice — Tier 2 — Action or response expected
CP102
Understanding your CP102 notice — Tier 2 — Action or response expected · 10-day window
CP104
Understanding your CP104 notice — Tier 2 — Action or response expected · 10-day window
CP105
Understanding your CP105 Notice — Tier 2 — Action or response expected
CP106
Understanding Your CP106 Notice — Tier 2 — Action or response expected
CP107
Understanding your CP107 notice — Tier 2 — Action or response expected
CP123
Understanding your CP123 notice — Tier 2 — Action or response expected
CP124
Understanding your CP124 notice — Tier 2 — Action or response expected · 30-day window
CP128
Understanding Your CP128 Notice — Tier 2 — Action or response expected
CP132
Understanding your CP132 notice — Tier 2 — Action or response expected
CP134B
Understanding your CP134B notice — Tier 2 — Action or response expected
CP14
Understanding your CP14 notice — Tier 2 — Action or response expected
CP140
Understanding your CP140 notice — Tier 2 — Action or response expected
CP14C
Understanding your CP14C notice — Tier 2 — Action or response expected
CP14D
Understanding your CP14D notice — Tier 2 — Action or response expected
CP14E
Understanding your CP14E notice — Tier 2 — Action or response expected
CP14F
Understanding your CP14F notice — Tier 2 — Action or response expected
CP14G
Understanding your CP14G notice — Tier 2 — Action or response expected
CP14H
Understanding your CP14H notice — Tier 2 — Action or response expected
CP14J
Understanding your CP14J notice — Tier 2 — Action or response expected
CP14K
Understanding your CP14K notice — Tier 2 — Action or response expected
CP15H
Understanding your CP15H notice — Tier 2 — Action or response expected
CP160
Understanding your CP160 notice — Tier 2 — Action or response expected
CP161
Understanding your CP161 notice — Tier 2 — Action or response expected
CP163
Understanding your CP163 notice — Tier 2 — Action or response expected
CP171
Understanding your CP171 notice — Tier 2 — Action or response expected
CP187
Understanding your CP187 notice — Tier 2 — Action or response expected
CP207
Understanding Your CP207 Notice — Tier 2 — Action or response expected · 45-day window
CP207L
Understanding Your CP207L Notice — Tier 2 — Action or response expected
CP210-OR-CP220
Understanding your CP210 or CP220 notice — Tier 2 — Action or response expected
CP21A
Understanding your CP21A notice — Tier 2 — Action or response expected
CP21H
Understanding your CP21H notice — Tier 2 — Action or response expected
CP22H
Understanding your CP22H notice — Tier 2 — Action or response expected
CP22I
Understanding your CP22I notice — Tier 2 — Action or response expected
CP256
Understanding your CP256 notice — Tier 2 — Action or response expected
CP2813
Understanding your CP2813 notice — Tier 2 — Action or response expected
CP40
Understanding your CP40 notice — Tier 2 — Action or response expected
CP501
Understanding your CP501 notice — Tier 2 — Action or response expected
CP501H
Understanding your CP501H notice — Tier 2 — Action or response expected
CP503
Understanding your CP503 notice — Tier 2 — Action or response expected
CP503H
Understanding your CP503H notice — Tier 2 — Action or response expected
CP504
Understanding your CP504 notice — Tier 4 — Escalation warranted · 30-day window · Escalation flag
CP504B
Understanding your CP504B notice — Tier 4 — Escalation warranted · 30-day window · Escalation flag
CP508C
Understanding your CP508C notice — Tier 4 — Escalation warranted · Escalation flag
CP51A
Understanding your CP51A notice — Tier 2 — Action or response expected
CP545
Understanding your CP545 notice — Tier 2 — Action or response expected · 30-day window
CP56
Understanding your CP56 notice — Tier 2 — Action or response expected
CP60
Understanding your CP60 notice — Tier 2 — Action or response expected
CP62
Understanding your CP62 notice — Tier 2 — Action or response expected
CP71A
Understanding your CP71A notice — Tier 2 — Action or response expected
CP71D
Understanding your CP71D notice — Tier 2 — Action or response expected
LP47
Understanding Your LP47 Notice — Tier 1 — Routine
LP60
Understanding Your LP60 Notice — Tier 2 — Action or response expected · 30-day window
LP64
Understanding Your LP64 Notice — Tier 1 — Routine
LT14
Understanding your LT14 notice — Tier 2 — Action or response expected
LT17
Understanding Your LT17 Notice — Tier 2 — Action or response expected
LT33
Understanding your LT33 notice — Tier 2 — Action or response expected
LT38
Understanding your LT38 notice — Tier 2 — Action or response expected
LT39
Understanding your LT39 notice — Tier 2 — Action or response expected
LT40
Understanding your LT40 notice — Tier 2 — Action or response expected
LT50
Understanding your LT50 notice — Tier 2 — Action or response expected
Letter 1175-3079-OR-289-REGARDING-MILITARY-DEFERMENT
Understanding your Letter 1175, 3079, or 289 regarding military deferment — Tier 2 — Action or response expected
Letter 2800C
Understanding your letter 2800C — Tier 2 — Action or response expected · 60-day window
Letter 6539C
Understanding your letter 6539C — Tier 2 — Action or response expected · 30-day window
Letter 725-B
Understanding your letter 725-B — Tier 2 — Action or response expected
CP22
CP 22a — Tier 2 — Action or response expected
Letter 16
What does this mean to me? — Tier 2 — Action or response expected
Letter 5972C
Letter 5972C — Tier 2 — Action or response expected
Installment agreement and collection alternatives
CP14IA
Understanding your CP14IA notice — Tier 2 — Action or response expected
CP166
Understanding your CP166 notice — Tier 2 — Action or response expected
CP508R
Understanding your CP508R notice — Tier 2 — Action or response expected
CP521
Understanding your CP521 notice — Tier 1 — Routine
CP522
Understanding your CP522 notice — Tier 4 — Escalation warranted · Escalation flag
CP522P
Understanding your CP522P notice — Tier 4 — Escalation warranted · Escalation flag
CP523
Understanding your CP523 notice — Tier 4 — Escalation warranted · 30-day window · Escalation flag
CP523H
Understanding your CP523H notice — Tier 4 — Escalation warranted · 30-day window · Escalation flag
CP71
Understanding your CP71 notice — Tier 2 — Action or response expected
CP71C
Understanding your CP71C notice — Tier 2 — Action or response expected
CP71H
Understanding your CP71H notice — Tier 2 — Action or response expected
LT19
Understanding your LT19 notice — Tier 2 — Action or response expected
LT24
Understanding your LT24 notice — Tier 2 — Action or response expected
LT27
Understanding your LT27 notice — Tier 2 — Action or response expected
Letter 6305
Understanding Your Letter 6305 — Tier 4 — Escalation warranted · Escalation flag
Letter 3820
Letter 3820 — Tier 2 — Action or response expected
Letter 4388
Letter 4388 — Tier 2 — Action or response expected
Penalty notices
CP141R
Understanding Your CP141R Notice — Tier 1 — Routine
CP142
Understanding your CP142 notice — Tier 2 — Action or response expected · 30-day window
CP14I
Understanding your CP14I notice — Tier 2 — Action or response expected
CP15B
Understanding your CP15B notice — Tier 4 — Escalation warranted · 60-day window · Escalation flag
CP162
Understanding your CP162 notice — Tier 2 — Action or response expected
CP162A
Understanding Your CP162A Notice — Tier 2 — Action or response expected
CP162B
Understanding your CP162B notice — Tier 2 — Action or response expected
CP162C
Understanding your CP162C notice — Tier 2 — Action or response expected
CP162E
Understanding your CP162E notice — Tier 2 — Action or response expected
CP165
Understanding Your CP165 Notice — Tier 2 — Action or response expected
CP173
Understanding your CP173 notice — Tier 2 — Action or response expected
CP173B
Understanding your CP173B notice — Tier 1 — Routine
CP183
Understanding Your CP183 Notice — Tier 2 — Action or response expected · 30-day window
CP2100-OR-CP2100A
Understanding your CP2100 or CP2100A Notice — Tier 2 — Action or response expected
CP211C
Understanding your CP211C notice — Tier 2 — Action or response expected
CP215
Understanding your CP215 notice — Tier 2 — Action or response expected
CP216H
Understanding your CP216H notice — Tier 2 — Action or response expected
CP220J
Understanding Your CP220J Notice — Tier 3 — Time-sensitive response
CP232B
Understanding Your CP232B notice — Tier 2 — Action or response expected
CP232C
Understanding your CP232C notice — Tier 2 — Action or response expected
CP232D
Understanding your CP232D notice — Tier 2 — Action or response expected
CP233J
Understanding your CP233J notice — Tier 3 — Time-sensitive response
CP235
Understanding your CP235 notice — Tier 2 — Action or response expected
CP238
Understanding Your CP238 Notice — Tier 1 — Routine
CP239
Understanding your CP239 notice — Tier 2 — Action or response expected
CP276B
Understanding Your CP276B Notice — Tier 1 — Routine
CP283
Understanding Your CP283 Notice — Tier 2 — Action or response expected
CP283C
Understanding your CP283C notice — Tier 2 — Action or response expected
CP295
Understanding Your CP295 Notice — Tier 2 — Action or response expected
CP30
Understanding Your CP30 Notice — Tier 2 — Action or response expected
CP30A
Understanding your CP30A notice — Tier 1 — Routine
CP30B
Understanding your CP30B notice — Tier 2 — Action or response expected
CP321A
Understanding your CP321A notice — Tier 1 — Routine
CP503J
Understanding your CP503J notice — Tier 3 — Time-sensitive response
CP504J
Understanding your CP504J notice — Tier 4 — Escalation warranted · 30-day window · Escalation flag
CP543
Understanding your CP543 notice — Tier 2 — Action or response expected · 30-day window
CP544
Understanding your CP544 notice — Tier 2 — Action or response expected
CP590
Understanding your CP590 notice — Tier 2 — Action or response expected · Escalation flag
CP75C
Understanding your CP75C notice — Tier 2 — Action or response expected
CP972F
Understanding Your CP972F Notice — Tier 2 — Action or response expected
Letter 226-J
Understanding your letter 226-J — Tier 3 — Time-sensitive response · 30-day window
Letter 227
Understanding your letter 227 — Tier 3 — Time-sensitive response
Letter 2802C
Understanding your 2802C letter — Tier 2 — Action or response expected
Letter 3176C
Understanding your letter 3176C — Tier 2 — Action or response expected · 30-day window
Underreporter / income matching
CP03
Understanding your CP03 notice — Tier 2 — Action or response expected
CP2000
Understanding your CP2000 series notice — Tier 3 — Time-sensitive response · 30-day window
CP2057
Understanding your CP2057 notice — Tier 2 — Action or response expected
CP230
Understanding your CP230 notice — Tier 2 — Action or response expected · 30-day window
CP240
Understanding your CP240 notice — Tier 2 — Action or response expected · 30-day window
CP2501
Understanding your CP2501 notice — Tier 3 — Time-sensitive response · 30-day window
CP2566
Understanding your CP2566 notice — Tier 2 — Action or response expected
CP2566R
Understanding your CP2566R notice — Tier 3 — Time-sensitive response
CP276A
Understanding your CP276A notice — Tier 1 — Routine
CP28
Understanding your CP28 notice — Tier 2 — Action or response expected
CP3219A
Understanding your CP3219A notice — Tier 4 — Escalation warranted · 90-day window · Escalation flag
CP531
Understanding your CP531 notice — Tier 2 — Action or response expected
CP538
Understanding your CP538 notice — Tier 2 — Action or response expected
CP539
Understanding your CP539 notice — Tier 3 — Time-sensitive response
CP540
Understanding your CP540 notice — Tier 2 — Action or response expected
CP546
Understanding your CP546 notice — Tier 2 — Action or response expected
CP87C
Understanding your CP87C notice — Tier 2 — Action or response expected
CP87D
Understanding your CP87D notice — Tier 2 — Action or response expected
Letter 2030
Understanding Your Letter 2030 — Tier 3 — Time-sensitive response
Letter 2531
Understanding your letter 2531 — Tier 3 — Time-sensitive response
Letter 3219B
Understanding Your Letter 3219B — Tier 4 — Escalation warranted · 90-day window · Escalation flag
Letter 6115C
Understanding your letter 6115C — Tier 2 — Action or response expected
90 Day Notice of Deficiency
90 Day Notice of Deficiency — Tier 4 — Escalation warranted · 90-day window · Escalation flag
Letter 3219
Letter 3219 Notice of Deficiency — Tier 4 — Escalation warranted · 90-day window · Escalation flag
Letter 3219-C
Letter 3219-C — Tier 4 — Escalation warranted · 90-day window · Escalation flag
Filing and non-filer
CP080B
Understanding your CP080B notice — Tier 2 — Action or response expected
CP081B
Understanding your CP081B notice — Tier 2 — Action or response expected
CP120A
Understanding Your CP120A Notice — Tier 2 — Action or response expected
CP120B
Understanding your CP120B notice — Tier 2 — Action or response expected
CP141L
Understanding Your CP141L Notice — Tier 2 — Action or response expected
CP169
Understanding your CP169 notice — Tier 2 — Action or response expected
CP211A
Understanding your CP211A notice — Tier 1 — Routine
CP212
Understanding your CP212 notice — Tier 1 — Routine
CP214
Understanding Your CP214 Notice — Tier 1 — Routine
CP250A
Understanding your CP250A notice — Tier 2 — Action or response expected · 30-day window
CP250B
Understanding your CP250B notice — Tier 1 — Routine
CP250C
Understanding your CP250C notice — Tier 2 — Action or response expected · 30-day window
CP255
Understanding Your CP255 Notice — Tier 2 — Action or response expected
CP259
Understanding your CP259 Notice — Tier 2 — Action or response expected
CP259A
Understanding Your CP259A Notice — Tier 2 — Action or response expected
CP259B
Understanding Your CP259B Notice — Tier 2 — Action or response expected
CP259D
Understanding Your CP259D Notice — Tier 2 — Action or response expected
CP259F
Understanding Your CP259F Notice — Tier 2 — Action or response expected
CP259G
Understanding Your CP259G Notice — Tier 2 — Action or response expected
CP259H
Understanding Your CP259H Notice — Tier 2 — Action or response expected
CP261
Understanding your CP261 notice — Tier 1 — Routine
CP262
Understanding Your CP262 Notice — Tier 2 — Action or response expected
CP264
Understanding Your CP264 Notice — Tier 1 — Routine
CP265
Understanding Your CP265 Notice — Tier 2 — Action or response expected
CP281
Understanding Your CP281 Notice — Tier 2 — Action or response expected
CP282
Understanding Your CP282 Notice — Tier 2 — Action or response expected
CP287
Understanding your CP287 notice — Tier 2 — Action or response expected
CP291
Understanding Your CP291 Notice — Tier 2 — Action or response expected
CP292
Understanding Your CP292 Notice — Tier 2 — Action or response expected
CP299
Understanding Your CP299 Notice — Tier 2 — Action or response expected
CP515
Understanding your CP515 notice — Tier 2 — Action or response expected
CP516
Understanding your CP516 notice — Tier 2 — Action or response expected
CP518
Understanding your CP518 notice — Tier 3 — Time-sensitive response
CP518-BUSINESS
Understanding Your CP518 Business notice — Tier 2 — Action or response expected
CP59
Understanding your CP59 notice — Tier 2 — Action or response expected
CP59R
Understanding your CP59R notice — Tier 2 — Action or response expected
CP63
Understanding your CP63 notice — Tier 2 — Action or response expected
CP81
Understanding your CP81 notice — Tier 2 — Action or response expected
CP88
Understanding your CP88 notice — Tier 2 — Action or response expected
LT18
Understanding your LT18 notice — Tier 2 — Action or response expected
LT26
Understanding your LT26 notice — Tier 2 — Action or response expected
LT41
Understanding your LT41 notice — Tier 2 — Action or response expected
LT51
Understanding your LT51 notice — Tier 2 — Action or response expected
Letter 4617C
Understanding your letter 4617C — Tier 2 — Action or response expected · 30-day window
Letter 5747C
Understanding your letter 5747C — Tier 2 — Action or response expected
Letter 5938
Understanding Your Letter 5938 — Tier 2 — Action or response expected
Letter 6436C
Understanding your letter 6436C — Tier 2 — Action or response expected · 30-day window
Letter 6483C
Understanding your letter 6483C — Tier 2 — Action or response expected
Refund claims and litigation
CP320B
Understanding your CP320B notice — Tier 4 — Escalation warranted · Escalation flag
CP74
Understanding your CP74 notice — Tier 1 — Routine
CP79
Understanding your CP79 notice — Tier 2 — Action or response expected
CP79A
Understanding your CP79A notice — Tier 2 — Action or response expected
CP79B
Understanding your CP79B notice — Tier 2 — Action or response expected
Letter 105-C
Letter 105 C — Tier 4 — Escalation warranted · Escalation flag
Letter 106-C
Letter 106 C — Tier 4 — Escalation warranted · Escalation flag
Letter 1277
Letter 1277 — Tier 4 — Escalation warranted · Escalation flag
Identity verification
CP01
Understanding your CP01 notice — Tier 1 — Routine
CP01A
Understanding your CP01A notice — Tier 1 — Routine
CP01C
Understanding your CP01C notice — Tier 1 — Routine
CP01E
Understanding your CP01E notice — Tier 1 — Routine
CP01H
Understanding your CP01H notice — Tier 2 — Action or response expected
CP01S
Understanding your CP01S notice — Tier 1 — Routine
CP01U
Understanding your CP01U notice — Tier 1 — Routine
CP209
Understanding Your CP209 Notice — Tier 1 — Routine
CP2809
Understanding your CP2809 notice — Tier 1 — Routine
CP303
Understanding your CP303 notice — Tier 2 — Action or response expected
CP304
Understanding your CP304 notice — Tier 1 — Routine
CP310
Understanding Your CP310 Notice — Tier 1 — Routine
CP311
Understanding your CP311 notice — Tier 1 — Routine
CP311A
Understanding your CP311A notice — Tier 2 — Action or response expected
CP53D
Understanding your CP53D notice — Tier 1 — Routine
CP542
Understanding your CP542 notice — Tier 1 — Routine
CP54B
Understanding Your CP54B Notice — Tier 2 — Action or response expected
CP54E
Understanding Your CP54E Notice — Tier 2 — Action or response expected
CP54G
Understanding Your CP54G Notice — Tier 2 — Action or response expected
CP54Q
Understanding your CP54Q notice — Tier 2 — Action or response expected
CP560A
Understanding your CP560A notice — Tier 1 — Routine
CP561A
Understanding your CP561A notice — Tier 2 — Action or response expected
CP561B
Understanding your CP561B notice — Tier 2 — Action or response expected
CP561C
Understanding your CP561C notice — Tier 2 — Action or response expected
CP562A
Understanding your CP562A notice — Tier 2 — Action or response expected · 60-day window
CP562C
Understanding your CP562C notice — Tier 2 — Action or response expected · 60-day window
CP563
Understanding your CP563 notice — Tier 2 — Action or response expected
CP563F
Understanding your CP563F notice — Tier 2 — Action or response expected
CP563G
Understanding your CP563G notice — Tier 2 — Action or response expected
CP565
Understanding your CP565 notice — Tier 1 — Routine
CP566
Understanding your CP566 notice — Tier 2 — Action or response expected
CP567
Understanding your CP567 notice — Tier 2 — Action or response expected
CP59SN
Understanding your CP59SN notice — Tier 2 — Action or response expected
CP6042
Understanding your CP6042 notice — Tier 2 — Action or response expected · 30-day window
Letter 12C
Understanding your Letter 12C — Tier 2 — Action or response expected · 20-day window
Letter 2801C
Understanding your letter 2801C — Tier 2 — Action or response expected · 30-day window
Letter 4281C
Understanding your letter 4281C — Tier 2 — Action or response expected
Letter 4310C
Understanding your letter 4310C — Tier 2 — Action or response expected
Letter 4883C
Understanding your letter 4883C — Tier 2 — Action or response expected
Letter 6167C
Understanding your letter 6167C — Tier 2 — Action or response expected · 30-day window
Letter 5071-C
Letter 5071C — Tier 2 — Action or response expected
Letter 5216C
Letter 5216C — Tier 2 — Action or response expected
Refund and adjustment
CP02
Understanding your CP02 notice — Tier 2 — Action or response expected
CP04
Understanding your CP04 notice — Tier 1 — Routine
CP05
Understanding your CP05 notice — Tier 2 — Action or response expected
CP05B
Understanding your CP05B notice — Tier 2 — Action or response expected
CP07
Understanding your CP07 notice — Tier 2 — Action or response expected
CP08
Understanding your CP08 notice — Tier 1 — Routine · 30-day window
CP09
Understanding your CP09 notice — Tier 1 — Routine
CP10
Understanding your CP10 notice — Tier 1 — Routine
CP103
Understanding Your CP103 Notice — Tier 2 — Action or response expected · 60-day window
CP108
Understanding your CP108 notice — Tier 1 — Routine
CP11
Understanding your CP11 notice — Tier 2 — Action or response expected
CP111
Understanding your CP111 notice — Tier 1 — Routine
CP112
Understanding your CP112 notice — Tier 1 — Routine
CP113
Understanding your CP113 notice — Tier 1 — Routine
CP114
Understanding your CP114 notice — Tier 1 — Routine
CP115
Understanding your CP115 notice — Tier 1 — Routine
CP116
Understanding Your CP116 Notice — Tier 1 — Routine · 60-day window
CP117
Understanding Your CP117 Notice — Tier 1 — Routine · 10-day window
CP12
Understanding your CP12 notice (including CP12, CP12E, CP12F, CP12G, CP12N, and CP12U) — Tier 1 — Routine
CP125
Understanding your CP125 notice — Tier 1 — Routine · 30-day window
CP126
Understanding Your CP126 Notice — Tier 1 — Routine
CP127
Understanding Your CP127 Notice — Tier 1 — Routine
CP12G-OR-CP12U
Understanding your CP12G or CP12U notice — Tier 1 — Routine
CP13
Understanding your CP13 notice — Tier 1 — Routine
CP130
Understanding Your CP130 Notice — Tier 1 — Routine
CP131
Understanding your CP131 notice — Tier 1 — Routine
CP131A
Understanding your CP131A notice — Tier 1 — Routine
CP133
Understanding your CP133 notice — Tier 1 — Routine
CP134R
Understanding your CP134R notice — Tier 1 — Routine
CP147
Understanding your CP147 notice — Tier 1 — Routine · 60-day window
CP153
Understanding your CP153 notice — Tier 1 — Routine
CP156
Understanding your CP156 notice — Tier 1 — Routine
CP16
Understanding your CP16 notice — Tier 1 — Routine
CP21B
Understanding your CP21B notice — Tier 1 — Routine
CP21C
Understanding your CP21C notice — Tier 1 — Routine
CP21I
Understanding your CP21I notice — Tier 2 — Action or response expected
CP225
Understanding your CP225 notice — Tier 1 — Routine
CP22A
Understanding your CP22A notice — Tier 2 — Action or response expected
CP23
Understanding your CP23 notice — Tier 2 — Action or response expected
CP231
Understanding your CP231 notice — Tier 1 — Routine
CP237
Understanding Your CP237 Notice — Tier 1 — Routine
CP237A
Understanding your CP237A notice — Tier 1 — Routine
CP24
Understanding your CP24 notice (including CP24, CP24E, CP24G, and CP24U) — Tier 1 — Routine
CP24G-OR-CP24U
Understanding your CP24G or CP24U notice — Tier 1 — Routine · 60-day window
CP25
Understanding your CP25 notice — Tier 1 — Routine
CP267
Understanding your CP267 Notice — Tier 1 — Routine
CP267A
Understanding your CP267A notice — Tier 1 — Routine
CP268
Understanding Your CP268 Notice — Tier 1 — Routine · 30-day window
CP27
Understanding your CP27 notice — Tier 1 — Routine
CP32
Understanding your CP32 notice — Tier 1 — Routine
CP321D
Understanding your CP321D notice — Tier 2 — Action or response expected
CP32A
Understanding your CP32A notice — Tier 1 — Routine
CP330
Understanding your CP330 notice — Tier 1 — Routine
CP3501
Understanding your CP3501 notice — Tier 1 — Routine
CP39
Understanding your CP39 notice — Tier 1 — Routine
CP42
Understanding your CP42 notice — Tier 1 — Routine
CP45
Understanding your CP45 notice — Tier 1 — Routine
CP49
Understanding your CP49 notice — Tier 1 — Routine
CP51B
Understanding your CP51B notice — Tier 1 — Routine
CP51C
Understanding your CP51C notice — Tier 1 — Routine
CP53
Understanding your CP53 notice — Tier 1 — Routine
CP53A
Understanding your CP53A notice — Tier 1 — Routine
CP53B
Understanding your CP53B notice — Tier 1 — Routine
CP53E
Understanding your CP53E notice — Tier 1 — Routine · 30-day window
CP87A
Understanding your CP87A notice — Tier 1 — Routine
CP87B
Understanding your CP87B notice — Tier 2 — Action or response expected
CP99A
Understanding your CP99A notice — Tier 1 — Routine
CP99B
Understanding your CP99B notice — Tier 1 — Routine
CP99C
Understanding your CP99C notice — Tier 1 — Routine
CP99D
Understanding your CP99D notice — Tier 1 — Routine
Letter 4464C
Understanding your letter 4464C — Tier 2 — Action or response expected
Letter 6312
Understanding Your Letter 6312 — Tier 1 — Routine
Letter 6416-A / Letter 6416
Understanding Your Letter 6416 or Letter 6416-A — Tier 1 — Routine
Letter 6417
Understanding your letter 6417 — Tier 1 — Routine
Letter 6419
Understanding your letter 6419 — Tier 1 — Routine
Letter 6475
Understanding your letter 6475 — Tier 1 — Routine
Letter 6550
Understanding Your Letter 6550 — Tier 1 — Routine
Letter 6591
Understanding Your Letter 6591 — Tier 1 — Routine
Account and informational
CP136
Understanding your CP136 notice — Tier 1 — Routine
CP136B
Understanding your CP136B notice — Tier 1 — Routine
CP137
Understanding your CP137 notice — Tier 1 — Routine
CP137A
Understanding Your CP137A Notice — Tier 1 — Routine
CP137B
Understanding Your CP137B Notice — Tier 1 — Routine
CP145
Understanding your CP145 notice — Tier 1 — Routine
CP148A
Understanding your CP148A notice — Tier 1 — Routine
CP148B
Understanding your CP148B notice — Tier 1 — Routine
CP152
Understanding your CP152 notice — Tier 1 — Routine
CP152A
Understanding your CP152A notice — Tier 1 — Routine
CP153W
Understanding your CP153W notice — Tier 1 — Routine
CP2006
Understanding your CP2006 notice — Tier 1 — Routine
CP216F
Understanding Your CP216F Notice — Tier 1 — Routine
CP217
Understanding your CP217 notice — Tier 1 — Routine
CP218
Understanding your CP218 notice — Tier 1 — Routine
CP219
Understanding your CP219 notice — Tier 1 — Routine
CP232A
Understanding your CP232A notice — Tier 1 — Routine
CP236
Understanding your CP236 notice — Tier 1 — Routine
CP248
Understanding your CP248 notice — Tier 1 — Routine
CP277
Understanding your CP277 notice — Tier 1 — Routine
CP279
Understanding Your CP279 Notice — Tier 1 — Routine
CP279A
Understanding Your CP279A Notice — Tier 1 — Routine
CP284
Understanding your CP284 notice — Tier 1 — Routine
CP286
Understanding Your CP286 Notice — Tier 1 — Routine
CP288
Understanding your CP288 notice — Tier 1 — Routine
CP290
Understanding Your CP290 Notice — Tier 1 — Routine
CP3500
Understanding your CP3500 notice — Tier 1 — Routine
CP44
Understanding your CP44 notice — Tier 1 — Routine
CP52
Understanding your CP52 notice — Tier 1 — Routine
CP53C
Understanding your CP53C notice — Tier 1 — Routine
CP53W
Understanding your CP53W notice — Tier 1 — Routine
CP547
Understanding Your CP547 Notice — Tier 1 — Routine
CP560B
Understanding your CP560B notice — Tier 1 — Routine
CP76
Understanding your CP76 notice — Tier 1 — Routine
CP84
Understanding your CP84 notice — Tier 1 — Routine
Letter 1278
Letter 1278 — Tier 1 — Routine
Letter 1802C
Letter 1802C — Tier 1 — Routine
Letter 2682
Letter 2682 — Tier 1 — Routine
Letter 4383
Letter 4383 — Tier 1 — Routine
Letter 4993
Letter 4993 — Tier 1 — Routine
Letter 5100
Letter 5100 — Tier 1 — Routine
Letter 5145
Letter 5145 — Tier 1 — Routine
Letter 913
Letter 913 — Tier 1 — Routine
Levy Release
Levy Release — Tier 1 — Routine
Levy Relief
Levy Relief — Tier 1 — Routine
Levy/Seizure of Assets
Levy/Seizure of Assets — Tier 1 — Routine
Lien Discharge
Lien Discharge — Tier 1 — Routine
Lien Release
Lien Release — Tier 1 — Routine
Lien Relief
Lien Relief — Tier 1 — Routine
Lien Subordination
Lien Subordination — Tier 1 — Routine