Payroll Tax Filing Checklist

Pull every active employee in Gusto / ADP / Rippling and confirm a current Form W-4 is on file. Cross-check state withholding equivalents (NY IT-2104, CA DE 4, etc.) for any employee who changed work state during the quarter. Missing or stale W-4s default to single / zero — a frequent under-withholding source.

Confirm every new hire from the period has a completed Form I-9 within 3 business days of start, and E-Verify case closure where state law requires it. Tie the HRIS new-hire roster to the payroll system's employee list — orphan records in either system signal a missed onboarding step.

Run the SSA Business Services Online verification on any new SSNs. Confirm home addresses match state of residence — a remote employee who moved states mid-quarter triggers multi-state withholding obligations and is the most common W-2 reissue cause.

Tie the payroll register's gross-wage total to the wage expense accounts in QuickBooks / NetSuite for the period. Variances usually trace to manual checks posted outside payroll, off-cycle bonus runs, or expense reimbursements miscoded as wages.

Recalculate employer-side Social Security (6.2% to wage base) and Medicare (1.45% + 0.9% Additional Medicare over $200K). Confirm SUI is calculated against each state's wage base — these change annually and are a common Q1 miss.

Verify Section 125 cafeteria, 401(k) deferrals, HSA, and commuter deductions reduced the correct tax bases (FIT vs FICA differ for some). Confirm group-term life over $50K is imputed and GTL imputed income is taxed for FICA. These drive W-2 box 12 codes at year-end.

Populate lines 1-15 from the quarterly payroll register. Reconcile line 12 (total taxes after adjustments) to actual deposits made (line 13a) — any imbalance becomes a balance due or overpayment that must be addressed before filing. Confirm Schedule B is attached if you are a semiweekly depositor.

File the appropriate state withholding return (e.g., NY NYS-45, CA DE 9 / DE 9C, IL IL-941) and SUI wage report for every state with active employees. Multi-state employers commonly miss states where one remote employee was hired mid-quarter.

Cover PA local EIT and LST, OH RITA / CCA municipalities, NYC, Philadelphia wage tax, and any other local jurisdictions where employees worked. Locals are the most-missed filings — a single PA employee can trigger filings in three jurisdictions (state, school district, municipality).

Verify whether the company is a monthly or semiweekly depositor based on the prior-year lookback period. If accumulated tax liability hits $100K on any day, the next-day deposit rule applies — missing this triggers a 10% penalty.

Initiate the EFTPS payment by 8:00 PM ET the business day before the due date — same-day submissions can fail and trigger late-deposit penalties. Watch for federal holidays that shift the semiweekly schedule.

Use each state's portal (NY PrompTax, CA EDD e-Services, IL MyTax, etc.) and any local lockbox or third-party processor (Berkheimer, RITA). Capture confirmation numbers in the workpaper for the audit trail.

Transmit through the payroll provider or MeF-approved software. 941 is due the last day of the month following quarter-end (Apr 30, Jul 31, Oct 31, Jan 31). Filings made via timely deposits in full receive a 10-day extension on the form itself, but the deposits themselves must still be on time.

At Q4, the sum of the four 941s must tie to the W-3 totals for FIT, Social Security wages, and Medicare wages. SSA / IRS reconciliation notices (CP-2100, Notice 972CG) are triggered when these don't match — fix before W-2 transmittal, not after.

W-2s and the W-3 transmittal are due to employees and SSA by January 31 — the same deadline for both copies. Confirm box 12 codes (D for 401(k), DD for employer health, W for HSA) reconcile to the deduction registers.

Pull every vendor paid $600+ for services with a current W-9 on file. Exclude payments made via credit card or third-party processor — those are reported on 1099-K by the processor. Missing W-9s at year-end is a common cause of backup-withholding scramble.