Multiple W-2s From One Year: Excess SS Tax and 401(k) Limits

If a merger or acquisition left you with two W-2s covering a single year at what felt like the same job, file both of them separately and watch four things: excess Social Security withholding, the Additional Medicare Tax, your total 401(k) contributions, and whether the wage totals across the forms match your final pay stub. Getting multiple W-2s from a merger is normal when the acquiring company operates under a different Employer Identification Number, and most of the reconciliation work is straightforward once you know where money tends to leak.

From your side, nothing changed on the acquisition date. From the IRS’s side, one legal employer stopped paying you and another started. That is why the year gets split into a “before” W-2 from the predecessor and an “after” W-2 from the successor, each under its own EIN.¹ In some deals the successor takes over the predecessor’s reporting and issues a single consolidated W-2 for the full year; if that happened, you have only one form and can skip most of what follows.²

Excess Social Security Tax You Can Get Back

This is where the money usually is. For 2026, Social Security tax applies to the first $184,500 in wages at 6.2%, capping the employee contribution at $11,439.00.³ When two employers report your wages in the same year, each payroll system may start counting from zero, and if your combined earnings clear the wage base you can end up paying Social Security tax above the annual maximum.

Federal law tells the successor’s payroll system to pick up the predecessor’s wage base when the successor acquires substantially all of the predecessor’s business property and immediately employs the same workers.⁴ Payroll systems don’t always implement that correctly, especially in rushed transitions or partial-asset deals, so verify it yourself.

Add Box 4 (Social Security tax withheld) from each W-2. If the combined figure exceeds $11,439.00, the overage is a refundable credit on Schedule 3, Line 11 of Form 1040.⁵ One boundary matters here: this credit only applies when the over-withholding came from having more than one employer. If a single employer over-withheld on its own, you can’t claim it on your return; the employer has to correct it, and if it refuses you file Form 843 with the IRS.⁶

Additional Medicare Tax You May Now Owe

The 0.9% Additional Medicare Tax runs in the opposite direction. Each employer is only required to withhold it once your wages with that specific employer pass $200,000 in the year.⁷ When a merger splits your income, neither W-2 alone may cross that trigger even though your total does, so neither employer withheld the additional tax.

You reconcile on Form 8959. Add Box 5 across every W-2 for total Medicare wages, and Box 6 for regular Medicare tax withheld; the form calculates what you owe and credits what was already taken out.⁸ The filing-status thresholds are $200,000 for single, $250,000 for married filing jointly, and $125,000 for married filing separately. They are not indexed to inflation and do not change year to year.

Check Your 401(k) Before April 15

The highest-stakes item in a merger year isn’t a payroll tax at all. It’s your retirement contributions. The 2026 elective deferral limit is $24,500, with an $8,000 catch-up for employees age 50 and older, and $11,250 for those aged 60 through 63.⁹

When the successor starts a new plan, it has no visibility into what you contributed at the predecessor. If you were deferring aggressively before the deal closed, your combined contributions can quietly exceed the annual limit. The IRS requires you to aggregate elective deferrals across every plan you participated in during the year.¹⁰

Uncorrected excess deferrals are taxed twice: once in the year contributed, and again when the money is distributed from the plan. To avoid that, request a corrective distribution of the excess (plus any earnings on it) by April 15 of the year after the excess occurred. That deadline is firm and does not move if you extend your return.¹⁰ Going forward, give the successor’s HR or benefits team the exact figure you already deferred at the predecessor so your contribution rate is set correctly from your first paycheck.

How to File the Return

Enter each W-2 as a separate record in your tax software, exactly as issued. Don’t combine numbers yourself; the software needs the distinct EINs and wage amounts to calculate the excess Social Security credit and to flag Additional Medicare Tax.

Once every form is in, the software should carry any Social Security overage to Schedule 3, Line 11 automatically.⁵ If your combined Medicare wages clear the threshold for your filing status, Form 8959 should populate as well; confirm the total Medicare wages on that form equal the sum of Box 5 across all your W-2s.⁸

Before you submit, run one sanity check. Add Box 1, Box 3, and Box 5 across every W-2 and compare each total to your final pay stub of the year. Numbers that don’t match usually mean a data-entry slip or a reporting mistake by one employer, and it is much easier to fix before filing than after.

If a W-2 Is Missing or Wrong

Predecessor companies sometimes dissolve after a deal closes, and the HR function goes with them. If a W-2 hasn’t arrived by early February, start with the successor employer; in some deals they took over the predecessor’s reporting and owe you a consolidated form, and even when they didn’t, their HR team can usually locate the right contact.

If the form still hasn’t arrived by the end of February, call the IRS at 800-829-1040 and the agency will reach out to the employer for you. As a last resort, file Form 4852 as a substitute, using your final pay stub from the predecessor and explaining on the form how you arrived at each figure.¹¹ If the real W-2 shows up later with different numbers, amend the return on Form 1040-X.

For a W-2 that arrives with errors, ask the employer for a corrected Form W-2c. If 30 days pass without a response, Form 4852 is available for that situation too.¹²

What to Have in Front of You

Every W-2 from the year. Check Box b for each EIN and Box c for the employer name; two different EINs confirms two separate legal employers rather than a duplicate.¹²
Your final pay stub from the predecessor. It shows year-to-date wages, Social Security withholding, and 401(k) deferrals through the closing date, and it’s the fastest way to verify the predecessor’s W-2.
Your first pay stub from the successor. If year-to-date totals reset to zero, you are reconciling two forms; if they carried over, you should be receiving one consolidated W-2.
Year-end statements from both 401(k) plans. Add the deferrals and compare against the $24,500 limit for 2026 (plus any catch-up you’re entitled to).⁹

Keep those records for at least three years after you file. If the IRS later questions the excess Social Security credit or your retirement contributions, they are the proof that the numbers came out of a corporate restructuring rather than a mistake on your return.

1
Internal Revenue Service. When to Get a New EIN
2
Internal Revenue Service. Revenue Procedure 2004-53
3
Social Security Administration. Contribution and Benefit Base
4
Office of the Law Revision Counsel. 26 USC 3121 – Definitions
5
Internal Revenue Service. 2025 Schedule 3 (Form 1040)
6
Internal Revenue Service. 2025 Instructions for Form 1040
7
Internal Revenue Service. Questions and Answers for the Additional Medicare Tax
8
Internal Revenue Service. Instructions for Form 8959
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Internal Revenue Service. 401(k) Limit Increases to $24,500 for 2026; IRA Limit Increases to $7,500
10
Internal Revenue Service. Consequences to a Participant Who Makes Excess Deferrals to a 401(k) Plan
11
Internal Revenue Service. About Form 4852, Substitute for Form W-2, Wage and Tax Statement, or Form 1099-R
12
Internal Revenue Service. 2026 General Instructions for Forms W-2 and W-3