Hired my first out-of-state employee and now finding out it might create tax filing obligations in another state

I run a small B2B services company structured as an S-Corp in Ohio. Until this year, everyone working for the business was local.

In January, I converted one of our long-time contractors into a full-time W-2 employee. They work remotely from Pennsylvania as a backend developer. We set up PA payroll withholding and unemployment through our payroll provider and thought that was the end of it.

Last week another business owner mentioned that having a W-2 employee in another state can create business tax filing requirements beyond payroll, even if that employee isn't selling anything and never meets with clients.

That caught me off guard because we're considering hiring another remote employee later this year, and now I'm trying to figure out whether we've accidentally opened up a much bigger compliance issue.

For context:

• Ohio S-Corp
• Around $450k annual revenue
• One remote employee in Pennsylvania
• Employee is purely operational (software development)
• No office, inventory, or customers in Pennsylvania

For anyone who has dealt with this, did adding a remote employee force you to file business returns in that state? Or was payroll registration enough?

I'm less worried about the paperwork and more worried about discovering a year from now that I've been missing some filing requirement I didn't even know existed.