First off, it’s important to make sure your payroll provider will automate federal, state, and local tax filings and payments. But on top of that, check to see who assumes the responsibility if a mistake is made. You should be offered an accuracy guarantee that puts the responsibility on the provider if they make a mistake.
Both Gusto and Paychex file and pay all federal, state, and local taxes, but neither offer an accuracy guarantee. So if they miss a filing or make a mistake, you would be financially responsible for fixing it. There are other providers that offer an accuracy guarantee as part of their full-service payroll offering (so you can rest knowing things are done right).