Written by James Chae — Co-Founder, Expert Sapiens
Reviewed March 2026
Tax
Definition
An IRS notice is official written communication from the IRS about your tax account — informing you of a balance due, audit, proposed adjustment, request for information, or other action. Each notice has a specific CP or LT number that identifies its type and the required response. Ignoring IRS notices escalates enforcement action.
Common IRS notices include: CP2000 (proposed changes based on third-party information mismatches — most common notice), CP501/CP503/CP504 (balance due notices in escalating severity), CP90/LT11 (final notice of intent to levy), LT16 (return delinquency), and audit notification letters (various). The response deadline is typically 30–60 days and is strictly enforced — missing it forfeits your right to contest. Not all notices require immediate payment: many are informational, propose adjustments you can contest, or request documentation. The CP2000 is especially important — it proposes changes based on W-2, 1099, or other information the IRS received that doesn't match your return, but the proposed amount often overstates liability before deductions are factored in. Notices are sent by postal mail to your last known address; they do not arrive by email or phone. Any 'IRS agent' calling by phone is a scam.
IRS notices are time-sensitive — missing response deadlines can result in automatic assessments, loss of appeal rights, and aggressive collection action. A tax advisor or enrolled agent can interpret the notice, determine if you actually owe what is claimed, prepare a response, and represent you before the IRS if needed.
Written by James Chae — Co-Founder, Expert Sapiens
Reviewed March 2026