States use the terms "Technology Model" and "Model One", "Model Two" and "Model Four" seller. What do those terms mean?
Answer:  States use these terms to identify which sellers use a Certified Service Provider (CSP) or a Certified Automated System (CAS).  


The Technology Models are:

A “Model One” seller is a “volunteer seller” that has contracted with a Certified Service Provider (CSP) to perform all the seller's sales and use tax functions, other than the seller's obligation to remit tax on its own purchases.   

A “Model Two” seller is a seller that has contracted with a provider to use their CAS.  A CAS is designed for a business that wants to use the tax calculation software that has been certified by the states while keeping the responsibility for filing returns and remitting the tax. 

A “Model Three” seller has a proprietary system that calculates tax due for each jurisdiction that meets the performance standards set by the states.  A seller must have a certain level of sales and a proprietary system that calculates tax due for each jurisdiction.

A “Model Four” seller does not use a CSP or a CAS.