A coworker once caught a $3,200 error on her pay stub. She'd been getting the wrong health insurance deduction — $150 per pay period too much — for almost a full year. Nobody at payroll had noticed. She only caught it because she was applying for a mortgage and, for the first time in years, actually had to read her stubs carefully.
This is the dirty secret of payroll: errors happen more often than people realize, and most of them go undetected because nobody reads their pay stubs past the net pay number. Payroll systems are reliable at the macro level but imperfect at the edge cases, and the edge cases are where your money lives.
Here are seven errors I've personally seen (or seen others catch) that show up more often than you'd expect. Call it a field guide to checking your own stubs.
1. Wrong benefits deduction amount
This is the most common error I've heard about. You elect a particular level of coverage at open enrollment — say, family health insurance at $350 per paycheck — and your actual deduction comes out to $400, or $300, or some other number that doesn't match.
How it happens: your election was entered incorrectly into the payroll system, or a rate change (open enrollment, qualifying life event) didn't process correctly.
How to catch it: multiply your pay-period deduction by 26 (or your pay frequency). Does it match the annual total you were told to expect at open enrollment? If not, something's off.
The nasty part: once an error has been running for months, you might be owed thousands of dollars in refunded deductions. It's worth catching early.
2. Old deductions that didn't stop
You change your 401(k) contribution percentage, cancel a voluntary benefit, drop your dental coverage, or stop a charitable payroll contribution. Weeks later, the old deduction is still coming out.
How it happens: the change form got lost, or was entered into the wrong system, or was processed for a different pay period. Payroll errors involving change requests are disturbingly common.
How to catch it: after you submit any change, check the next one or two pay stubs. Did the change take effect? If not, follow up immediately. The longer a phantom deduction runs, the harder it is to untangle.
3. Overtime calculated wrong
Overtime rules are more complicated than most people realize. In most jurisdictions, overtime kicks in at 40 hours per workweek (not per pay period), paid at 1.5x your "regular rate." The regular rate isn't just your base hourly rate — it includes certain bonuses, shift differentials, and other compensation.
How it goes wrong: the payroll system uses the wrong workweek boundary (if your workweek runs Sunday-Saturday but payroll counts Monday-Sunday, weekends can be miscategorized), or it uses your base rate instead of your regular rate for overtime calculations, or it splits overtime across pay periods incorrectly.
How to catch it: if you worked overtime in a period, verify the calculation. Your overtime pay should equal (hours over 40) × (regular rate × 1.5). If the math doesn't work, dig in.
Federal Department of Labor enforcement actions over wage and hour violations are not rare — a meaningful number of them come from exactly this kind of error.
4. Wrong state tax withholding
If you moved states during the year, or if you work remotely in a different state than your employer, your state tax withholding can be wildly wrong. I've seen people pay California income tax while living in Nevada (no state income tax) because nobody updated their address in payroll.
How it happens: payroll systems default to the employer's state, or to an old address that never got updated, or to the employee's work state even when they live somewhere else and are taxed there.
How to catch it: look at your state withholding line. Is the state code correct for where you live? Is the rate reasonable for that state?
The correction can be complex if you've been paying into the wrong state's system for months. You'll probably need to file returns in both states to sort it out. Better to catch it in January than September.
5. Health savings account (HSA) contribution errors
HSA contributions have specific annual limits (different for single vs family coverage, with a catch-up allowance at age 55+). Employers can contribute, employees can contribute, and the total has to stay under the annual cap.
How it goes wrong: you elect an HSA contribution that, combined with your employer's contribution, exceeds the annual limit. The payroll system doesn't always catch this. You end up with an excess contribution that creates tax problems.
How to catch it: at year-end, your YTD HSA contribution (your own + employer's) should be at or below the annual limit. If it's over, you need to withdraw the excess before your tax filing deadline or face a 6% excise tax.
6. Missing retroactive pay
You get a raise effective April 1, but the paperwork didn't process until April 15. The April 1-15 period was paid at the old rate, and the difference should be paid as "retro pay" on a later stub.
How it goes wrong: the retro calculation is missed, or the retro pay is processed as regular pay (which affects how tax withholding is calculated), or the retro amount is wrong.
How to catch it: if you know you got a raise that took effect partway through a pay period, verify that a retro adjustment appears on a subsequent stub. If it never does, ask HR.
This one is particularly painful because retro pay often doesn't appear on the YTD total unless it's processed as a separate line item — meaning your W-2 might understate your earnings.
7. Phantom hours or wrong hours
Hourly employees sometimes see hours on their stubs that don't match what they actually worked. Usually it's a small discrepancy — a few hours one way or the other — and it's usually a timekeeping system error rather than malice.
How it happens: the timekeeping system rounds in unexpected ways, or a punch wasn't recorded correctly, or a manager approved the wrong timesheet.
How to catch it: compare your actual hours worked (you should be keeping your own rough records) against the hours on your stub. If they don't match, flag it.
For salaried employees, hours usually don't appear on stubs, so this one doesn't apply. But if you're hourly or earn overtime, this is worth monitoring.
How to run your own pay stub audit
If you're going to do a more thorough review of your pay history, here's an approach that actually works.
Pull your last three months of pay stubs (or your whole year, if you're doing a year-end review). Put the key data into a spreadsheet — gross, taxes by type, each deduction, net pay, YTD totals. Either do this manually or use a tool; StubSheet (disclosure: I built it) is one option for converting PDFs to spreadsheet data, but pen-and-paper works too if you have the time.
Once you have the data in a table, patterns become obvious in a way they aren't when you're flipping through PDFs. A deduction that shouldn't be there jumps out. A tax withholding that dropped suddenly gets noticed. YTD totals that don't add up to the sum of individual periods become visible.
Most audit findings come from seeing the same data in a different format. The error was always there; you just couldn't see it in the PDF.
What to do when you find an error
Document it clearly. Screenshot the stub, circle the problem, write down what you expected and what the stub shows. This is what you'll send to payroll.
Contact payroll or HR with specific details. "My pay stub for period March 1-15 shows $300 in health insurance deduction; my enrolled plan is $200 per pay period. This appears to be an overcharge." Don't be vague.
Ask for a correction in writing. A verbal promise is fine, but you want something in writing to confirm the issue and the resolution.
Follow up on the next stub. Did the correction actually process? If not, escalate.
Keep records. If the error affects your W-2 or has tax implications, you might need documentation later. Save the email chain.
The short version
Pay stub errors are more common than people assume, and most go undetected because nobody reads their stubs. The most frequent errors are wrong benefits deductions, deductions that didn't stop after a change, miscalculated overtime, wrong state withholding, HSA over-contributions, missing retro pay, and incorrect hours. A monthly or quarterly audit using spreadsheet data instead of raw PDFs makes these errors visible. Catching them early is much easier than correcting them after a W-2 has been issued.