Why you might get Letter 12C
The IRS compares amounts reported on tax returns to information it receives from employers and payers (Forms W-2, 1099, and corrected forms like W-2c). When those records don’t match what you filed, the IRS can send Letter 12C — “Request for Additional Wage Information” — asking you to confirm the correct wage amounts and to send proof. Common triggers include employer reporting errors, missing W-2s, duplicate or incorrect 1099s, or math/entry mistakes on your return.
What the letter usually asks for
Letter 12C will typically include:
- A short explanation of the discrepancy and the tax year involved.
- The IRS’ recorded wage amount(s) and your reported amount(s).
- A deadline to respond (commonly 30 days from the date on the notice). Check the specific date on your letter.
- A list of acceptable documents to prove wages — for example, copies of Form W-2, Form 1099, a corrected W-2 (W-2c), pay stubs, or an employer statement on company letterhead.
- Instructions for where and how to send the documentation and a contact phone number if you have questions.
Important: keep copies of everything you send. Do not mail original W-2s unless the notice explicitly requests originals.
Immediate steps to take when you receive Letter 12C
1) Read the letter carefully. Note the tax year, the amounts in dispute, and the response deadline.
2) Compare the IRS figures to your tax return and your own records (W-2s, 1099s, pay stubs). Also check your Wage and Income Transcript (you can order one from the IRS) to see what forms the IRS has on record. If you need help understanding transcripts, see our glossary entry on Wage and Income Transcript: https://finhelp.io/glossary/wage-and-income-transcript/.
3) Contact your employer or payer if the IRS information looks wrong. Ask for a copy of the original W-2 or a corrected W-2 (Form W-2c). If the employer agrees the original was wrong, they can issue a W-2c — and you’ll need that to correct your return if necessary. For more on correcting wages and withholding, see: https://finhelp.io/glossary/correcting-wages-or-withholding-with-form-1040-x-and-w-2c/.
4) If the IRS is correct and your return has an error, prepare to amend your tax return using Form 1040-X. The IRS explains Form 1040-X and when to file it here: https://www.irs.gov/forms-pubs/about-form-1040-x.
5) If you believe the IRS record is incorrect but can’t get immediate proof from an employer (e.g., employer out of business), include a written explanation and supporting documentation you do have (pay stubs, bank records) and explain efforts you made to obtain the official forms.
How to respond and what to include
- Include a cover letter that references Letter 12C by its date and any notice number shown.
- Attach copies (not originals) of W-2s, W-2c, 1099s, pay stubs, employer letters, or corrected information. If you file an amended return (Form 1040-X), include a copy of the amended return and the corrected forms that support the change.
- If someone else is responding on your behalf, include a signed Form 2848 (Power of Attorney) or signed permission from you. Details: https://www.irs.gov/forms-pubs/about-form-2848.
- Send documents to the address on the letter (or follow directions for faxing or secure upload if provided). Mail using tracked delivery when possible.
Timelines and potential outcomes
- Response time: Most IRS notices give around 30 days to respond, but always follow the date on your specific letter.
- If you respond with proof the IRS wage record is wrong, they will correct their records and update your account. If the employer issues a W-2c, you may need to file Form 1040-X to correct your return for that year.
- If you do not respond, the IRS may adjust your return to match its records. That can result in additional tax owed, reduced refunds, or disallowance of credits that depend on wages (like the Earned Income Tax Credit).
- If the IRS adjusts your return and you disagree, you have appeal rights — instructions will be included with the adjustment notice.
Common complications and how to handle them
Employer uncooperative or out of business
- Document attempts to reach the employer (emails, calls, certified mail). If the employer won’t cooperate or is out of business, provide alternate proof such as pay stubs and bank deposit records showing pay amounts and dates.
- Consider requesting the IRS to accept substitute documentation; include a clear explanation in your response.
Missing or late W-2
- If you never received a W-2, request a copy from your employer. If the employer doesn’t provide one, call the IRS at the number on the letter for guidance. You may be able to use Form 4852 (Substitute for Form W-2) when you file an amended return; see IRS instructions for Form 4852.
If the letter affects a tax credit
- Wage-related discrepancies can affect credits (EITC, child tax credit, etc.). If an adjustment could reduce or eliminate a credit, respond quickly with proof to avoid an incorrect denial or reduced refund.
When to get professional help
If the situation is complex (multiple years involved, employer refuses to issue W-2c, or the tax change is large), consider a tax pro or an IRS-authorized representative. The Taxpayer Advocate Service is an independent IRS organization that can help if you’re experiencing financial difficulty or if the IRS isn’t resolving your problem. More on contacting the Taxpayer Advocate is on the IRS site.
Recordkeeping and future prevention
- Keep copies of all W-2s, 1099s, and pay stubs for at least three years after filing (longer if you file claims for refunds or if an issue arises).
- Check your Wage and Income Transcript early in the filing season to verify the IRS received correct information from employers and payers: https://finhelp.io/glossary/wage-and-income-transcript/.
- Review your final pay stub for year-to-date wage totals to catch employer reporting issues quickly.
Related FinHelp resources
- Correcting Wages or Withholding with Form 1040-X and W-2c: https://finhelp.io/glossary/correcting-wages-or-withholding-with-form-1040-x-and-w-2c/
- Form W-2: Wage and Tax Statement (how W-2s work): https://finhelp.io/glossary/form-w-2-wage-and-tax-statement/
- Waiver for Incorrect Employer-Reported Wages: https://finhelp.io/glossary/waiver-for-incorrect-employer-reported-wages/
- Abatement for Incorrect Wages Reported: https://finhelp.io/glossary/abatement-for-incorrect-wages-reported/
- Form 433-A: Collection Information Statement (if collection action follows): https://finhelp.io/glossary/form-433-a-collection-information-statement-for-wage-earners-and-self-employed-individuals/
Useful external references
- IRS — Respond to a notice or letter: https://www.irs.gov/individuals/respond-to-a-notice-or-letter
- IRS — About Form 1040-X: https://www.irs.gov/forms-pubs/about-form-1040-x
- IRS — About Form W-2c: https://www.irs.gov/forms-pubs/about-form-w-2c
- IRS — About Form 2848 (Power of Attorney): https://www.irs.gov/forms-pubs/about-form-2848
Final checklist before you send your response
- Copy the Letter 12C date and notice number on your cover letter.
- Include clear, legible copies of supporting documents (W-2, W-2c, pay stubs).
- Keep a copy of everything you mail and use tracked delivery.
- If you can’t provide the requested form, include a written explanation and substitute documents showing the wage history.
If you’d like, FinHelp can draft a short cover letter template you can use when responding to Letter 12C or help you decide whether an amended return is needed.