IRS notices and letters
Every page here starts from the notice the client received: what program sent it, what clock it started, what happens if the clock runs out, and the response that works, with the IRM section the IRS employee working the case follows.
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CP2000 (underreporter proposal)
The IRS matched the return against Forms W-2 and 1099 and proposes a change. Not a bill, but silence leads to a notice of deficiency.
CP2501 (underreporter inquiry)
An AUR inquiry asking the taxpayer to explain an income or payment mismatch before the IRS proposes tax on a CP2000.
CP11 (math error, balance due)
The IRS used math error authority to change the return and assess tax. The taxpayer has 60 days to demand abatement.
CP12 (math error, refund change)
The IRS used math error authority and the result is an overpayment that differs from what the return claimed.
CP14 (first balance due)
The first bill after an assessment. It is the IRC 6303 notice and demand that starts the collection notice stream and creates the federal tax lien if unpaid.
CP501 (balance due reminder)
A reminder notice sent because the first bill was not paid or answered. No new rights, but the stream is moving toward a levy notice.
CP503 (second reminder)
The second reminder of an unpaid balance. The next notice in the stream is the CP504 notice of intent to levy.
CP504 (notice of intent to levy)
The fourth notice in the stream and the statutory notice of intent to levy. It allows state refund levies after 30 days but is not the CDP notice.
LT11 / Letter 1058 (CDP levy notice)
The final notice before levy on wages, bank accounts and other property. It starts the 30-day window to request a collection due process hearing.
LT16 (please call us)
An Automated Collection System letter asking for contact about unpaid taxes, unfiled returns or both. Enforcement can follow.
CP90 (FPLP levy notice)
The Federal Payment Levy Program's CDP notice, issued when a federal payment matches an unpaid account. It starts a 30-day hearing window.
CP71 (annual balance reminder)
The yearly reminder the IRS must send on delinquent accounts. Variants cover currently not collectible accounts, queued accounts and accounts with revenue officers.
CP22A (adjustment, balance due)
An Accounts Management adjustment notice showing a balance due. The source and reason codes tell you why the account changed.
CP59 (no return on file)
The first IMF return delinquency notice. Unresolved cases get a CP518 and then move to ACS or the Automated Substitute for Return program.
CP161: business balance due
The first bill on most business returns. The IRS made no math correction; tax, penalties or interest are simply unpaid.
CP162 series: 1065/1120-S penalties
Since 2022 the CP162 is the e-file penalty notice, the CP162A is the late filing penalty and the CP162B is the missing information penalty.
CP215: civil penalty assessed
Notice and demand for a miscellaneous civil penalty posted to a separate civil penalty module, often from W-2 reconciliation or an examiner's Form 8278.
CP3219A: AUR 90-day letter
The notice of deficiency issued after a CP2000 goes unanswered or unresolved. The 90-day Tax Court clock is statutory and cannot be extended.
Letter 3219: 90-day letter
The campus examination's notice of deficiency. It starts the 90-day Tax Court clock after a Letter 525 went unanswered or unresolved.
Letter 525: 30-day letter
The campus examination's proposed report. It is the last stop before the notice of deficiency and the last easy route to Appeals.
Letter 950: field 30-day letter
The revenue agent's unagreed report with 30 days to request Appeals. A protest that meets Publication 5 is the ticket to an Appeals conference.
Letter 566: mail audit begins
The campus examination's opening letter, asking for documents on specific items. A good response here often ends the audit.
Letter 2205: field audit begins
The revenue agent's letter asking the taxpayer to call and schedule a field examination. 2205-A lists the issues; 2205-D is for partnerships.
Letter 1153: proposed TFRP
The preliminary notice the IRS must deliver before assessing the trust fund recovery penalty against a responsible person. A timely protest gets a pre-assessment Appeals hearing.
Letter 3172: lien filed (CDP)
The collection due process notice for a lien filing. The hearing request deadline is printed on the letter and is computed from the lien filing date, not the letter date.
Letter 5071C: verify identity
A Taxpayer Protection Program letter. The return is held until the taxpayer verifies; a representative with a Form 2848 for the year can authenticate by phone.
CP2057: possible missing income
An Automated Underreporter soft notice with no tax proposal and no case. It asks the taxpayer to check the return and amend if income was omitted.
Letter 226-J: ACA employer penalty
The IRS's first proposal of an employer shared responsibility payment to an applicable large employer, built from Forms 1094-C and 1095-C and employees' premium tax credits.
Notice decoder
A searchable list of IRS notice and letter numbers with what each means and the clock it starts.
How to respond to a notice
The order of operations for a client's IRS notice, with the statutory and administrative clocks side by side.
CP518 (final notice, no return)
The last IMF return delinquency notice. About six weeks later the module goes to TDI status 03 and can be assigned to ACS or the Automated Substitute for Return program.
CP521 (IA payment reminder)
The routine monthly reminder on an IDRS-monitored installment agreement. Harmless when paid; a skipped payment and a second miss lead to the CP523 default notice.
CP523 (IA default notice)
Sent by certified mail when an agreement defaults. The agreement terminates 30 days after the notice date unless the default is cured; Form 9423 appeal rights run before and after termination.
CP05 (refund held for review)
A RIVO pre-refund hold on wages, withholding or credits. The CP05 asks for nothing; the CP05A asks for pay stubs and employer letters. The IRM allows up to 180 days for the review.
CP23, CP24, CP25 (estimated payments)
Notice Review issues these when claimed estimated payments differ from the account by $1 or more. A payment discrepancy is not a math error; only an accompanying math error carries the 60-day abatement right.
CP75 series (EITC audit by mail)
The initial contact letter for a refundable credit exam under IRM 4.19.14. Documents go in with the Response form; no response leads to Letter 525, then a notice of deficiency, and possibly a 2-year ban.
CP2566 (ASFR 30-day proposal)
The ASFR program's 30-day letter. Tax is computed from Forms W-2 and 1099 at single or married filing separately rates with no credits; a filed return almost always beats it.
CP3219N (ASFR notice of deficiency)
The automated notice of deficiency for a non-filer. Ninety days to petition the Tax Court; a return filed in the window is accepted but does not extend the deadline.
CP259 (business return not filed)
The first business return delinquency notice. Each form and period gets its own CP259; unresolved cases get a CP518 and then ACS, the queue, a revenue officer or a 6020(b) return.
Letter 3164 (third-party contacts)
The IRC 7602(c) advance notice, in more than twenty versions, issued by exam and collection before contacting anyone other than the taxpayer. No response is required; the right it creates is the list of contacts.
Letter 4883C (identity verification)
A TPP letter: the return is unpostable until the taxpayer (or a Form 2848 representative authorized for the year) authenticates by phone. No online option; no Form 14039.
Letter 12C (return incomplete)
Issued from Submission Processing (Code and Edit or Error Resolution) on Form 6001 before the return posts. Reply with the exact items requested; a no-reply return is processed with the unsupported items removed.
Letter 105-C (claim disallowed)
The statutory notice of full claim disallowance, sent certified mail. It starts two years to sue in district court or the Court of Federal Claims; Appeals is available but does not stop the clock.
Letter 106-C (partial disallowance)
The partial version of the claim disallowance notice, used when the allowed part still produces a refund. The two-year suit period runs on the disallowed part; Appeals rights are printed automatically.
Letter 5040-J / CP220J (ESRP)
The follow-up and the bill in the IRC 4980H process. A 5040-J gives 15 days before the proposed payment is assessed; a CP220J means it has been assessed and is collectible like any other liability.
Forms, tools and templates
Transcript code decoder
Paste transcript lines and get the IRS's own definition of every transaction code and TC 971 action code, with practitioner notes on the ones that matter.
Client notice intake form
A one-page form for logging a client's IRS notice: identifiers, dates, amounts, deadlines, IRS contact and next steps, plus a deadline key by notice type.
CDP deadline calculator
Counts the 30-day CDP window and the one-year equivalent hearing window from a levy notice or lien filing, with weekend and holiday rules and the Tax Court deadline.