67 Pa. Code § 51.2
The following words and terms, when used in this chapter, have the following meanings, unless the context clearly indicates otherwise:
Extension fee-The portion of the fee mandated by 75 Pa.C.S. § 1314(d) (relating to transfer of registration) that is attributable to extending the expiration date. The extension fee shall be equal to the number of months from the previous expiration date to the new expiration date times the prorated monthly fee for the vehicle class.
Increase fee-The portion of the fee mandated by 75 Pa.C.S. § 1314(d) that is attributable to the upgrade in class of the vehicle. The increase fee shall be equal to the number of months from the issuance of the transfer to the expiration date of the registration times the difference in prorated monthly fees from the former class to the new class.
Transfer fee-The fee prescribed by 75 Pa.C.S. § 1927 (relating to transfer of registration).
67 Pa. Code § 51.2