Payroll is one of the few areas of a small business where a small mistake can turn into a genuinely expensive one — and often not right away. Misclassifications, missed deadlines, and setup errors tend to surface months later, as penalties, back pay, or an audit notice, long after the original mistake was made.
1. Misclassifying employees as contractors
This is one of the most common — and most costly — payroll mistakes. Worker classification depends on how much control you have over the work, not just what the agreement calls someone. Misclassifying an employee as a 1099 contractor can mean back payroll taxes, penalties, and benefits owed retroactively once it's caught.
2. Missing tax deposit deadlines
Payroll tax deposits run on their own schedule — separate from your regular filing deadlines — and it can be monthly or semi-weekly depending on your deposit history. Missing a deposit deadline triggers penalties that scale with how late the payment is, starting almost immediately.
3. Getting overtime calculations wrong
Overtime isn't always as simple as time-and-a-half past 40 hours. Bonuses, commissions, and certain other pay can affect the "regular rate" overtime is calculated from, and getting this wrong is a common source of back-pay claims.
4. Not keeping up with multi-state rules
If you have even one remote employee working from a different state than your business is registered in, that can create new withholding, unemployment insurance, and registration obligations in that state — rules that are easy to miss if payroll was set up before that employee was hired.
5. Treating payroll setup as a one-time task
Minimum wage changes, new hires, benefit elections, and shifting state rules all mean payroll isn't something you configure once and forget. A setup that was correct a year ago can be quietly wrong today without anyone noticing until a filing catches it.
Payroll is also one of the categories worth getting right in your chart of accounts — misclassified payroll expenses are a common source of a P&L that doesn't quite add up.
Every one of these mistakes is avoidable with the right setup and someone actually watching for the changes that affect it. Payroll is part of what S&C Bookkeeping handles for clients — not just running it, but keeping it correct as the rules and your team change. Get in touch if you want a second set of eyes on how yours is currently set up.