How Payroll Actually Works: A Small Business Guide

See It in Action First

Before we walk through the mechanics, this overview from a certified payroll instructor breaks down how a paycheck is built from the ground up — ideal context whether you're running payroll yourself or reviewing what your processor sends you.

Video: Educational overview of payroll mechanics for small business owners.

The IRS collected over $1.6 trillion in employment taxes in fiscal year 2023 — more than any other category of federal revenue (IRS 2024). Every dollar of that total passed through a business's payroll system first.

For small business owners, payroll is one of the most consequential financial processes you run. Get it right, and your employees are paid correctly, your taxes are deposited on time, and your filings are clean. Get it wrong, and you face penalties, back taxes, and the kind of employee trust problems that are hard to recover from.

This post explains how payroll actually works — not just the concept, but the precise sequence of calculations, obligations, and deadlines that govern every pay period. We'll cover gross wages, mandatory deductions, employer tax contributions, deposit schedules, and the filings that tie it all together. All figures reflect U.S. federal tax law as of 2026; Virginia employers should confirm state-specific rates with a qualified advisor.

Step 1 — Calculating Gross Wages

Gross wages are what an employee earns before any deduction is taken. The calculation depends on how the employee is compensated.

Step 2 — Employee Tax Withholdings

Once gross wages are established, several amounts are withheld from the employee's paycheck. These are deductions the employee owes; the employer collects them and remits them on the employee's behalf.

Federal Income Tax (FIT)

Determined by the employee's W-4 elections and the IRS withholding tables in Publication 15-T. The amount varies by filing status, pay period frequency, and any additional withholding the employee requests. There is no fixed percentage — it is calculated per pay period against the current year's tax brackets.

FICA — Social Security & Medicare

FICA splits into two taxes, both applied to gross wages:

• Social Security: 6.2% on wages up to the 2026 wage base of $176,100 (SSA 2025).
• Medicare: 1.45% on all wages, no cap. An additional 0.9% applies to wages over $200,000 (single filers), which the employer must begin withholding once that threshold is crossed in the calendar year.

State & Local Income Tax

Virginia imposes a graduated income tax with rates from 2% to 5.75% (Virginia Department of Taxation 2026). Withholding is calculated from the employee's VA-4 form. Some Virginia localities also levy a modest wage tax; verify your specific jurisdiction.

Step 3 — Employer Tax Contributions

Beyond withholding, employers owe their own share of taxes on top of gross wages. These are costs you bear — they do not come out of the employee's paycheck.

Step 4 — Pre-Tax and Post-Tax Deductions

Deductions beyond taxes reduce the employee's net pay, and their order in the calculation matters. Pre-tax deductions reduce taxable income; post-tax deductions do not.

Sources: IRS Publication 15 (2026); IRS Publication 969 (HSA & FSA rules).

Step 5 — Deposit Schedules & Filing Deadlines

Collecting taxes is only half the job. You must deposit them with the IRS on a schedule determined by your total tax liability from the prior lookback period. Late deposits carry penalties of 2–15% depending on how late they are (IRS 2026, Publication 15).

Source: IRS Publication 15 (Employer's Tax Guide), 2026 edition.

Annual & Quarterly Filing Requirements

Choosing a Pay Period: What the Numbers Actually Mean

Pay period frequency affects employee cash flow, your administrative burden, and how you accrue payroll liabilities on your books. There is no universally "best" frequency — but your choice has real downstream effects.

Source: American Payroll Association. 2024. Payroll Practice Fundamentals.

The Most Common Small Business Payroll Mistakes

The NFIB reports that payroll errors and related penalties cost small business owners billions annually (NFIB Research Foundation 2023). Most mistakes fall into a short list of recurring categories.

• Misclassifying employees as independent contractors. If the IRS reclassifies a 1099 worker as a W-2 employee, you owe all back FICA — both employee and employer shares — plus penalties.
• Missing deposit deadlines. Even one day late triggers a 2% penalty. Deposits more than 16 days late carry a 10% penalty (IRS 2026, Publication 15).
• Incorrect overtime calculations. Bonuses, shift differentials, and commissions must be included in the "regular rate" for overtime purposes under the FLSA — not just the base hourly rate.
• Stale W-4 data. Employees who haven't updated their W-4 in years may be under-withheld, creating tax bills and unhappy staff. The IRS redesigned the W-4 in 2020; employees who last filed before that date may benefit from an update.
• Using payroll software without understanding the output. Software automates calculations but cannot catch data-entry errors. A wrong hire date, wrong state, or wrong pay rate silently computes correctly — on the wrong number.

Action Steps