To legally bring the car home and register it, specific paperwork is required: Buying or Selling Your Vehicle in Pennsylvania - FACT SHEET
If you pay sales tax to the state of purchase, PA typically grants a credit for that amount. If the out-of-state tax is lower than PA's rate, you must pay the difference to PennDOT. buying a car out of state pa
Keep your original bill of sale to prove taxes were paid elsewhere. Essential Documentation and Title Transfer To legally bring the car home and register