The fundamental rule is simple. You generally withhold state income tax based on where the employee performs the work, not where your business is located. If your company is in Massachusetts but you have an employee working from home in New Hampshire, New Hampshire rules apply to that employee. This basic principle gets complicated quickly when you have people in multiple states.

Each state where you have employees requires separate registration. You’ll need to register for a state withholding account and a state unemployment insurance account. Some states combine these registrations. Others make you file with different agencies. The timelines vary too. Some states want you registered before the first paycheck goes out. Others give you 30 days after hiring.

State unemployment insurance rates differ dramatically. Massachusetts might charge you one rate while Texas charges another. Your experience rating in one state doesn’t transfer to another. You’re starting fresh as a new employer in each state you enter, which often means paying the new employer rate until you build up history.

Some states have reciprocity agreements with neighboring states. This matters when an employee lives in one state but works in another. Pennsylvania and New Jersey have reciprocity, for example, which simplifies things. Without reciprocity, you might need to withhold for the work state while the employee also owes taxes to their home state. They’ll get credit for what was withheld, but it creates complexity for everyone.

Local taxes add another layer in certain areas. Ohio has municipal income taxes in many cities. Pennsylvania has local earned income taxes. New York City has its own withholding. These aren’t optional. You’re required to withhold and remit just like state taxes.

Your payroll system needs to support multi-state processing. Not every platform handles this well. Managed payroll services that specialize in multi-state compliance will automatically calculate the correct withholding, file returns with each jurisdiction, and keep track of changing rates and rules. Trying to manage this manually with spreadsheets is asking for mistakes.

Year-end reporting gets more involved too. Each employee needs W-2s that correctly report wages and withholding by state. If someone moved mid-year or worked in multiple states, their W-2 needs to reflect that accurately.

The registration process alone takes time. Each state has its own forms, its own online portals, and its own processing timelines. Before your first payroll in a new state, you need the account numbers set up in your system. Rushing this leads to late filings and penalties right out of the gate.

Remote work has made this more common for small businesses. What used to be a concern only for large companies with multiple locations now affects any business that hires remote employees. One employee in another state triggers all of these requirements.

If you’re expanding into multiple states or already have employees scattered around, working with an Andover, MA payroll service that understands multi-state compliance will save you significant headaches. The rules change frequently, and what works in one state doesn’t necessarily apply in another. Getting it wrong means penalties, interest, and unhappy employees who discover their taxes weren’t handled correctly.