IRS NOTICE
CP11 — Math error adjustment (balance due)
The IRS found a calculation or math error on the return that results in additional tax owed. The taxpayer can dispute the IRS's correction within 60 days — if they don't respond, the assessment stands.
General information only. Not legal or tax advice.
Typical response window
Typically about 60 days. The IRS correction becomes final if unchallenged. If the client disputes it, the 60-day deadline is firm.
What the first hour looks like
Compare the IRS correction against the return line by line. If the client agrees, document the file. If the client disputes the IRS math, capture the 60-day deadline and route for a response decision.
Starter document checklist
- The CP11 notice
- The filed return for the tax period
- Records supporting the amounts the IRS corrected (W-2s, 1099s, supporting schedules)
- Documentation showing how the original amounts were calculated
- Prior IRS correspondence on this period
Do the whole first hour in one place
TaxRiskOS captures the notice, computes the deadline, builds the checklist, flags whether it needs partner or counsel review, and produces a clean handoff packet — the first hour, made repeatable. It documents process, not advice.