December pay stub shows an extra federal or state withholding line labeled true-up, reconciliation, or year-end adjustment. You had RSU vests during the year and wonder whether payroll is fixing supplemental withholding, catching up FICA, or something else entirely.
Start here
What you need before using this
- December or final pay stub of the year with YTD columns.
- All confirmations and pay stubs.
- Form W-4 on file with employer.
- gap calculator output for the year.
- Prior-year for comparison if true-up is new to you.
True-up labels and policies are employer-specific. Not all companies run year-end reconciliation.
Why this happens
Payroll systems track cumulative wages and . Year-end true-up entries may increase or decrease December to hit annual targets.
vests add mid-year. Flat supplemental on each may leave cumulative federal below what payroll policy expects for your W-4.
True-up lines appear on salary pay stubs, not always on isolated off-cycle stubs. Labels vary: TRUE-UP, RECON, YE ADJ, or internal codes.
State true-up may run separately from federal when state supplemental rules differ.
True-up increases December net pay reduction — it is cash withheld, not a new wage category by itself unless paired with a bonus or on the same check.
FICA true-up is less common for employees already at Social Security wage base but Medicare reconciliations can appear for high earners.
Employers may true-up only for employees above certain compensation levels.
True-up is not the same as a correction. reports annual totals; true-up is a payroll timing tool within the year.
If true-up withheld extra federal tax, you may see a larger refund or smaller balance due — but other income and deductions still affect the return.
Negative true-up (refund to paycheck) is possible when payroll over-withheld earlier.
-specific supplemental elections — if your plan allows higher flat rates — reduce need for year-end true-up at some companies.
Bonus and in the same year compound true-up amounts when payroll reconciles once in December.
Contractors on 1099-NEC do not receive employer true-up — this guide is for employees.
Document true-up pay stubs for cash-flow planning in December.
Box 2 should equal sum of federal tax lines on all pay stubs including true-up.
What to check
- True-up line amount on December stub vs YTD federal change.
- Whether a posted on same pay period.
- W-4 extra in Box 4(c) already set.
- gap estimate for full year including vests.
- State true-up line if applicable.
- Net pay change on final paycheck.
- Employer payroll FAQ or year-end email about reconciliation.
- January Boxes 2 and 17 vs expectations.
Assuming year-end true-up means RSU tax is fully paid
What to check in your documents
- Final pay stub with true-up line highlighted.
- All pay stubs from the year.
- Form W-4 submitted during the year.
- when issued.
- gap calculator worksheet.
December federal true-up after three RSU vests
Illustration only, not your tax situation.
Questions people ask
- What is payroll true-up on my pay stub?
- A year-end adjustment payroll uses to reconcile cumulative tax withheld with policy or W-4 targets. It is , not a new type of income.
- Is true-up related to RSU vests?
- Often indirectly — supplemental may leave a gap payroll tries to close in December. Not all employers true-up.
- True-up on W-2?
- shows total , not true-up separately. Sum of pay stubs should match Box 2.
- Can true-up reduce my paycheck?
- Yes. Extra lowers net pay in the true-up period.
- True-up vs estimated tax?
- True-up is employer . Estimated tax is your direct payment to IRS. Both count toward tax paid.
- Should I change W-4 instead of relying on true-up?
- Many employees set W-4 extra earlier in the year for predictable cash flow. See W-4 after guide.
- State true-up on RSU income?
- Possible where state payroll runs year-end reconciliation. Rules vary by employer and state.
- True-up and aggregate withholding?
- Different concepts. Aggregate is per-pay-period method on checks. True-up is year-end cumulative adjustment.
- Employer did not true-up — did I overpay?
- Not necessarily. You may owe at filing if supplemental was low. Run gap estimate.
- Which calculator after seeing true-up?
- gap calculator with full-year income and salary.
When to get help from a tax pro
- True-up amount seems larger than any reasonable shortfall.
- Box 2 does not match pay stub YTD after true-up.
- Multi-state payroll with unexplained reconciliation lines.
- December true-up with termination same month.
Related calculators
- RSU Withholding Gap Calculator
Focus on the gap between what your employer withholds on RSU vests and what you may owe when everything is reconciled.
- RSU Tax Calculator
Model federal and state taxes on your RSU vest, compare withholding to estimated tax, and see what you may keep.
- Annual RSU Income Estimator
Total your expected RSU ordinary income for the year — a starting point before running detailed tax estimates.
Related pages
- Reading Your Pay Stub After an RSU Vest
Vest FMV adds to gross wages on the same pay stub as salary — supplemental withholding and FICA lines spike, but net pay alone does not prove your full-year tax is covered.
- RSU Aggregate Withholding Explained
Aggregate withholding combines vest and salary wages on one pay period — federal withholding may follow W-4 tables instead of the flat supplemental rate.
- W-4 After RSU Vest
Updating Form W-4 to increase paycheck withholding is often simpler than quarterly estimated tax when RSU vest withholding fell short of your marginal rate.
- RSU Withholding vs Actual Tax
Why flat supplemental withholding on RSU vests often differs from your actual tax when salary, bonus, and vests stack in one year.
- RSUs on W-2: What to Look For
Your W-2 should reflect RSU vest income in wages — know which boxes to check before filing.
Sources and notes
Primary tax claims on this page are supported by the official and secondary sources below. Broker and software links describe reporting mechanics — confirm rules against IRS or state guidance.
Year-end payroll withholding reconciliation after RSU supplemental wages.
- IRS Publication 15 (Circular E) — Supplemental wages
Internal Revenue Service · Official
Section 7 describes supplemental wage withholding, including the optional 22% flat rate and 37% rate above $1 million of supplemental wages in a calendar year.
- IRS Publication 525 — Taxable and Nontaxable Income
Internal Revenue Service · Official
Covers compensation income from stock-based pay, including restricted property under section 83.
- Equity Compensation — RSU taxation at vest and on sale
Charles Schwab (Workplace Financial Services) · Brokerage explainer
Plain-language explainer: RSU value at vest on W-2, FICA, withholding may not cover full tax, separate capital gains on sale.
For learning, not filing
VestingTax.com is not a CPA firm or tax preparer. Grants, employers, and states all differ. Use the cited IRS and state sources above, your own documents, and a qualified tax professional before you make decisions from this guide.