IRS NOTICE REFERENCE
Understanding your CP173B notice
We reduced or removed the penalty for underpayment of estimated tax reported on your tax return because the penalty entered on your return exceeds the maximum amount we can legally charge.
General information only. Not legal or tax advice.
Notice details
- Notice code
- CP173B
- Category
- Penalty
- Severity tier
- Tier 1 — Routine. Informational or administrative notice; no response typically required.
- Governing law
- §6651; §6662; §6751 (Internal Revenue Code sections)
- Source
- IRS.gov — Understanding Your IRS Notice
What this notice is
We reduced or removed the penalty for underpayment of estimated tax reported on your tax return because the penalty entered on your return exceeds the maximum amount we can legally charge.
Source: IRS.gov. Reproduced for reference. General information — not legal or tax advice.
What the IRS says to do
Review the account information shown in your notice. Compare your records with ours, and if we removed or reduced your penalty in error, please return the refund with your explanation.
This is the IRS’s own guidance reproduced from the IRS notice page. It describes the IRS’s process — it is not legal or tax advice from TaxRiskOS.
Governing IRS procedure (Internal Revenue Manual)
The IRS’s own internal procedures for handling this notice type are documented in the Internal Revenue Manual:
Reference to published IRS procedure. General information — not legal or tax advice.
Official IRS reference
Read the official notice page on IRS.gov: https://www.irs.gov/individuals/understanding-your-cp173b-notice
Related tools
TaxRiskOS is workflow software for practitioners — it captures the notice, computes the deadline, surfaces the escalation tier, and builds a document checklist. It documents process; it does not give advice or draft responses.
Check this notice’s deadline (free tool)