Quick answer

When an employer made a mistake on the Form W‑2 they issued, the employer should file Form W‑2c to correct the record with the employee and the Social Security Administration. If you already filed your federal tax return before receiving a corrected W‑2, file Form 1040‑X to amend that return only when the correction changes your taxable income, withholding, or credits in a way that affects your tax liability or refund. (IRS: About Form W‑2c; IRS: About Form 1040‑X)

Why this matters

Wage-reporting errors affect your tax liability, Social Security earnings record, and eligibility for credits and benefits. An incorrect W‑2 left uncorrected can trigger IRS notices (for example, a CP2000), create a mismatch between IRS records and your return, or lead to underpaid tax with penalties and interest. Fixing the source (the W‑2) keeps SSA and IRS records aligned, while amending the return updates your tax calculation.

Sources: IRS pages for W‑2c and 1040‑X. See also the W‑2 instructions for employer filing rules (IRS W‑2 Instructions).

Step-by-step workflow for employees (practical)

  1. Check your W‑2 carefully when you receive it. Compare year-to-date pay stubs versus boxes 1–6 (Box 1: wages, Box 2: federal income tax withheld, Boxes 3–6: Social Security and Medicare wages and taxes). Also confirm name and SSN accuracy.
  2. If you see an error, contact your employer or payroll/HR immediately and request that they prepare a W‑2c. Employers are responsible for issuing the corrected Form W‑2c and for filing with the SSA.
  3. If you have not yet filed your tax return, wait for the corrected W‑2 if it will materially change your reported wages or withholding. If the W‑2c is delayed and you must file, keep documentation and use Form 4852 (Substitute for Form W‑2) only as a last resort. (IRS: Form 4852)
  4. If you already filed and the corrected W‑2 changes your tax outcome, prepare and file Form 1040‑X to amend. Typically you must amend to claim a larger refund or to pay additional tax. See IRS timelines below.
  5. Keep copies of the original W‑2, the W‑2c, correspondence with employer, and any amended returns.

Employer responsibilities and timing

  • Employers file Form W‑2c to correct errors on a previously filed W‑2 and send a copy to the employee. Employers also file Form W‑3c (Transmittal) when correcting electronically filed W‑2s with the SSA.
  • There is no single fixed deadline for filing a W‑2c — it should be filed as soon as an error is discovered. However, employers should correct and resubmit to avoid penalties for incorrect information returns. (See the IRS instructions for W‑2/W‑3 and penalties.)

For employer-side guidance and detailed steps, see FinHelp’s entry on Employer Responsibilities: Correcting W‑2 and 1099 Errors After Filing. (Internal link: Employer Responsibilities: Correcting W-2 and 1099 Errors After Filing)

When must you file Form 1040‑X?

File Form 1040‑X when a corrected W‑2 or other new information changes your filing in these ways:

  • Corrected wages or withholding change the tax you owe or your refund amount.
  • You need to change credits or deductions that affect tax liability.
  • You must report missing income that was later issued on a corrected information return.

Deadlines to claim refunds: generally three years from the original return filing date (including extensions) or two years from the date you paid the tax, whichever is later. If you’re amending to pay tax owed, do so promptly to limit penalties and interest. See the IRS About Form 1040‑X for details.

What if your employer refuses or is slow to issue a W‑2c?

If your employer does not correct a W‑2 in a reasonable time, you have options:

  • Document your attempts to obtain a corrected W‑2 (emails, calls, certified letters).
  • If the original W‑2 is missing or incorrect and you cannot obtain a W‑2c, you may file your return using Form 4852 (Substitute for Form W‑2) to estimate wages and withholding based on your pay stubs. Use Form 4852 only when necessary; the IRS may delay processing while it verifies.
  • You can also contact the IRS (and in some cases the state tax agency) for help getting a corrected W‑2 from the employer.

Cite: IRS Form 4852 instructions; IRS help for missing W‑2s.

Examples that clarify common scenarios

Example A — Employer error discovered before filing

  • Your original W‑2 reported $45,000 in Box 1; your payroll stub shows $54,000. You notify payroll and they issue a W‑2c correcting Box 1 and Box 2 withholding. You use the corrected W‑2 to file your federal return. No 1040‑X needed.

Example B — Corrected W‑2 issued after you filed

  • You filed your return showing $45,000 and received a $1,200 refund. Later you receive a W‑2c showing $54,000 and higher withholding. Recalculate your tax: if the corrected numbers raise additional tax owed, file Form 1040‑X to report the higher income and adjust tax. If the W‑2c increases withholding such that your refund is larger, file Form 1040‑X to claim the additional refund (subject to the refund time limit).

Example C — Employer recorded Social Security wages incorrectly

  • A W‑2 understated Social Security wages (Boxes 3/5). Employer issues W‑2c and files with SSA. While the correction typically does not change federal income tax, it affects your SSA earnings record. Confirm SSA records after correction.

State returns and other knock‑on effects

A corrected W‑2 can also affect state and local tax returns. If your state taxes were based on the original wage report, you may need to file a state amended return. Rules vary by state — check your state department of revenue and include state amendments when necessary.

Also monitor any potential IRS notices triggered by mismatches between information returns and your filed return. If you receive a notice, respond promptly with the requested documentation.

For how the IRS uses information returns to cross-check tax returns, see FinHelp’s guide How the IRS Uses Information Returns (1099s, W-2s) to Cross-Check Tax Returns. (Internal link: How the IRS Uses Information Returns (1099s, W-2s) to Cross-Check Tax Returns)

Practical tips and best practices (from practice)

  • Reconcile pay stubs to the W‑2 as soon as you receive it. Small errors are easier to fix early.
  • Keep a running folder (digital or paper) of yearly pay stubs and W‑2s.
  • If you receive a W‑2c, treat it as part of that tax year’s records even if it arrives late.
  • If amending is required, attach a copy of the corrected W‑2 (W‑2c) to the 1040‑X when it will help explain the change.
  • Use certified mail or tracked email when requesting corrections from payroll so you have a record.
  • If you expect a refund from an amended return, note the IRS can take several months to process 1040‑X filings.

Common mistakes to avoid

  • Don’t assume a small discrepancy doesn’t matter. Even modest underreported wages can trigger notices and interest.
  • Don’t file a duplicate 1040 for the same year; use Form 1040‑X for corrections.
  • Don’t try to file a W‑2c yourself — only the employer may file a W‑2c and submit corrections to the SSA.

Helpful IRS references and further reading

And see FinHelp articles linked above for employer-side corrections and information‑return matching.

Bottom line

Correct the source first: ask your employer to file a W‑2c whenever a W‑2 contains incorrect wages, Social Security/Medicare wages, withholding, or personal data. File Form 1040‑X only when the corrected W‑2 (or other new information) changes your tax calculation or refund. If your employer won’t cooperate, use Form 4852 and contact the IRS for assistance.

Professional disclaimer: This article is educational and not tax advice. For guidance tailored to your situation, consult a CPA, enrolled agent, or tax attorney. All IRS citations current as of 2025.