How to use the decoder
Paste lines from an account transcript pulled through the Transcript Delivery System or a Tax Pro Account, or type codes separated by spaces. The decoder reads the three-digit code at the start of each line and any code written as TC 123, then shows the IRS's own title and remarks from Document 6209 for each master file the code is used on, followed by a plain-English note for the codes practitioners meet most. It reads codes only; check the transcript for the dates and amounts. Nothing you paste leaves the browser.
Document 6209 explains that “Transaction Codes (TC) consist of three digits.” Every transaction that posts to the master file carries one, so the transcript is a ledger: debits (tax, penalties, interest, refunds out) and credits (payments, credits, abatements). Penalty and interest codes usually come in pairs, with the abatement one number higher: TC 166 and 167 for the late-filing penalty, 276 and 277 for late payment, 196 and 197 for interest, 240 and 241 for a civil penalty. The decoder covers the 389 individual and business code rows in the public edition; lines the IRS marks for official use only are redacted there and are not included.
Which account the module is
A transcript covers one module, identified by its MFT (master file tax) code and tax period. The ones a representative sees most, from Document 6209 Section 2 and the penalty sections:
| MFT | Account |
|---|---|
| 30 | Form 1040 (individual income tax) |
| 31 | Individual modules split from MFT 30, for example to treat spouses on a joint return separately |
| 55 | Individual civil penalties, including the trust fund recovery penalty |
| 29 | IRA additional taxes (IRAF) |
| 01 | Form 941 |
| 02 | Form 1120 and 1120-S |
| 05 | Form 1041 |
| 06 | Form 1065 |
| 10 | Form 940 |
| 13 | Business civil penalties |
| 16 | Form 945 |
| 51 | Form 709 |
| 52 | Form 706 |
Codes to look for, by situation
| Question | Codes |
|---|---|
| When was the return filed and assessed? | 150 (and 976 or 977 for duplicate and amended returns); 460 for an extension |
| Is there an exam or underreporter case? | 420, 424, 922, 925; 494 for a notice of deficiency; 300 for the assessment |
| What penalties were charged and removed? | 166/167, 276/277, 176, 186/187, 240/241 |
| What stops or extends collection? | 480 (offer), 520 (litigation, bankruptcy, CDP), 530 (not collectible), 550 (CSED extended), 971 with action code 043 (pending installment agreement) |
| Where did the money go? | 610, 670, 806, 706, 826, 846, 898 |
| Is the representative on file? | 960 and 961 |
TC 971 is a flag whose meaning depends on its action code; the second box looks those up from Document 6209 Section 8C. Common ones: 043 (installment agreement pending), 063 (installment agreement in effect), 069 (CDP notice issued), 275 (timely CDP request received) and 035 (failure-to-pay trigger after a final notice). For the full method of reading a module, see reading an account transcript; for statute dates, the statute date calculator; for penalty amounts, the penalty and interest calculator. Payers decoding a Form 945 or civil penalty module can also use the TIN Comply transaction code decoder, which carries notes for backup withholding and Form 1099 penalties.
The edition matters. The IRS publishes Document 6209 annually, and the 2023 edition is the current one listed on its Document 6209 page as of October 2026; the decoder uses that edition's Sections 8A and 8C.
Questions practitioners ask
Why does my transcript show a code the decoder cannot find?
Some transaction codes and action codes are for official use only and are redacted from the public edition of Document 6209. Others are used only on files other than the individual and business master files; uncheck both boxes to search every file.
What does TC 971 mean on a transcript?
A miscellaneous transaction whose meaning depends on the action code next to it. Transcripts usually print a short description; type the action code in the second box for the IRS's definition. TC 972 with the same action code reverses it.
Which dates start the statutes?
The assessment of the return's tax (TC 150) starts a 10-year collection period under IRC 6502 from the assessment date, and each later assessment, such as a TC 290, TC 300 or a penalty, starts its own. The assessment statute under IRC 6501 runs from the date the return was filed, not from the TC 150 date.
What does TC 960 do?
It adds the Centralized Authorization File indicator to the module. Document 6209 says it causes notices and/or refunds to be sent to the authorized representative. TC 961 reverses it and zeros the indicator.