Identify the notice, isolate the requested action, and compare the IRS figures with the return, transcript, and payment record before choosing a response.
Choose the page that matches the actual notice, form, enforcement step, decision, record problem, or term—not merely the broadest phrase. Each guide states the file to build, the distinction to verify, common mistakes, and primary sources.
How to use this library
- Start with the exact name or number printed on the document.
- Confirm the taxpayer, entity, tax form, and tax period before combining records.
- Open the closest guide and build its issue-specific evidence list.
- Check the official source and the current instructions on the controlling document.
- Use a checklist to record delivery proof, follow-up, and unresolved questions.
Browse IRS Notices
CP11 Math Error Balance IRS Letter
Understand an IRS math-error change that produces a balance; compare the changed line with the filed return and supporting schedules.
CP12 Refund Adjustment IRS Letter
Understand an adjustment that changes the refund shown on the return; trace the adjustment before assuming the original refund calculation was accepted.
CP14 Balance Due IRS Letter
Understand an initial balance-due notice; verify the tax period, assessed tax, payments, penalties, and interest before choosing a payment response.
CP2000 Underreported Income IRS Letter
Understand a proposed change based on third-party income information; compare each listed information return with the filed return; a CP2000 is a proposal, not a bill to ignore.
CP22A Tax Change IRS Letter
Understand a change to the account after information supplied by the taxpayer; identify the request or amended filing that led to the change and verify how it posted.
CP23 Estimated Tax IRS Letter
Understand a mismatch involving estimated-tax payments; reconcile dates, amounts, taxpayer identification, and the tax year where each payment was applied.
CP2566 Substitute Return IRS Letter
Understand a proposed assessment when the IRS has no processed return on file; confirm whether a return was filed, rejected, misapplied, or still needs to be prepared.
CP49 Refund Applied IRS Letter
Understand a notice that a refund was applied to another federal tax debt; match the offset to the tax period and verify whether the underlying balance is correct.
CP501 Reminder Notice IRS Letter
Understand an early reminder of an unpaid balance; verify the balance and current notice sequence before enforcement notices arrive.
CP503 Second Reminder IRS Letter
Understand a later balance-due reminder; determine whether a payment, dispute, or arrangement is missing from the account.
CP504 Intent to Levy IRS Letter
Understand a notice warning of levy or offset action; treat the printed response instructions as urgent and distinguish this notice from a later collection-due-process notice.
CP518 Final Return Request IRS Letter
Understand a final request for an unfiled return; identify every missing period and whether the IRS already prepared or proposed figures.
CP59 Unfiled Return IRS Letter
Understand a notice that the IRS has no return on file; confirm the filing requirement and whether the return was filed under the correct identity and tax period.
CP71 Annual Balance IRS Letter
Understand an annual reminder that a balance remains; review how interest, penalties, payments, and any collection arrangement changed the account.
CP90 Final Notice IRS Letter
Understand a final levy notice that may include collection-due-process rights; read the hearing-rights section and use the exact deadline printed on the notice.
CP91 Social Security Levy IRS Letter
Understand a notice concerning levy action on Social Security benefits; check the benefit, tax period, hardship facts, and appeal instructions promptly.
Form 668 A Bank Levy IRS Letter
Understand a levy delivered to a bank or other holder of funds; confirm whose account is affected, the levy date, the tax periods, and any ownership or hardship issue.
Form 668 W Wage Levy IRS Letter
Understand a continuous levy directed to an employer or payer; review the tax periods, exemption paperwork, payroll effect, and release or appeal route.
Form 668 Y Tax Lien IRS Letter
Understand a Notice of Federal Tax Lien filing; separate the public lien filing from a levy and review release, withdrawal, discharge, subordination, or appeal questions.
Letter 1058 Final Notice IRS Letter
Understand a final notice of intent to levy with hearing rights; preserve the response deadline and identify the tax periods covered before proposing alternatives.
Letter 12C Missing Information IRS Letter
Understand a request for information needed to process a return; send only the listed items through the method stated in the letter and retain proof.
Letter 2205 Field Audit IRS Letter
Understand an examination contact or appointment letter; identify the examiner, tax periods, appointment details, and initial information-document request.
Letter 2800C Withholding IRS Letter
Understand a withholding-compliance letter affecting wage withholding; review the employer instructions, allowance status, and response channel before the effective date.
Letter 3172 Federal Tax Lien IRS Letter
Understand a notice of a federal tax lien filing and possible appeal rights; confirm the filing details and the deadline shown for any collection-due-process request.
Letter 3219 Deficiency Notice IRS Letter
Understand a statutory notice of deficiency often called a 90-day letter; treat the Tax Court petition date as separate from ordinary response or payment dates.
Letter 4883C Identity Verification IRS Letter
Understand an identity-verification request; use only the official verification channel listed in the letter and avoid sending identity documents to unrelated sites.
Letter 5071C Identity Verification IRS Letter
Understand an identity-verification request that may direct the taxpayer online or by phone; confirm the letter is authentic and use the IRS channel printed on it.
Letter 525 Examination Report IRS Letter
Understand an examination report and proposed changes; mark each item agreed, disputed, or still unsupported and read the protest instructions.
Letter 566 Audit Start IRS Letter
Understand a correspondence-examination opening letter; make an indexed response tied to each requested return item.
Letter 6331C Collection Contact IRS Letter
Understand an IRS collection contact letter; verify the employee or unit, the balance and periods, and the requested next contact.
Letter 692 Proposed Adjustment IRS Letter
Understand a letter communicating a proposed examination adjustment; compare the proposal with the examiner's workpapers and note agreement or disagreement by issue.
Letter 915 Exam No Change IRS Letter
Understand a notice that the examination closed with no change; retain the closing letter with the return and confirm which tax periods and issues it covers.
Letter 950 Thirty Day Letter IRS Letter
Understand a preliminary examination letter offering an administrative appeal route; use the protest instructions and deadline printed in the package.
LT11 Final Notice IRS Letter
Understand a final levy notice with collection-due-process information; identify every listed period and protect the hearing deadline shown on the notice.
Notice of Deficiency IRS Letter
Understand a statutory notice giving a route to petition the U.S. Tax Court; do not substitute an ordinary IRS letter for a timely petition when the notice requires court action.
Notice of Federal Tax Lien IRS Letter
Understand a public filing that secures the government's claim against property; distinguish lien filing, lien release, withdrawal, discharge, and subordination.
Notice of Levy IRS Letter
Understand an enforcement document directed to property or a third party; identify the property, holder, tax periods, delivery date, and any ownership or hardship issue.
Quality boundary
These pages do not estimate personal outcomes, rank private firms, or replace a credentialed review. When a deadline, levy, payroll tax, litigation, fraud concern, business shutdown risk, or sensitive spouse issue is present, preserve the date and consider qualified help promptly.
Official sources to verify
Rules, forms, addresses, thresholds, and deadlines can change. Check the current official page and the instructions printed on your own document before acting.
- IRS notices and lettersOfficial government, court, or taxpayer-assistance source.
- Taxpayer Bill of RightsOfficial government, court, or taxpayer-assistance source.
- Taxpayer Advocate ServiceOfficial government, court, or taxpayer-assistance source.