You need to charge sales tax in Pennsylvania if you have a sales tax nexus in the state.

A sales tax nexus means different things in different states. It can mean having a physical location (e.g. a brick and mortar store), or someone in the state working for you. For ecommerce it can also mean having an ‘affiliate’ or click through sales tax nexus.

To know for certain if you should be charging sales tax in Pennsylvania, check the Pennsylvania government sales tax website.

Some goods are exempt from sales tax in Pennsylvania for example groceries, most medical supplies and some items of clothing. You'll also find Pennsylvania sales tax exemptions which can be applied because the seller or purchaser meets certain criteria.

For a full list of exemptions, check the Pennsylvania government tax website.