When registering, the seller may select one of the following methods of remittances or other method allowed by state law to remit the taxes collected:
(A) MODEL 1, where a seller selects a CSP as an agent to perform all the seller’s sales or use tax functions, other than the seller’s obligation to remit tax on its own purchases.
(B) MODEL 2, wherein a seller selects a CAS to use which calculates the amount of tax due on a transaction.
(C) MODEL 3, wherein a seller utilizes its own proprietary automated sales tax system that has been certified as a CAS.