Streamlined Sales and Use Tax Agreement (SSUTA) 318: Section 318 Uniform tax returns

Each member state requires one return per taxing period per seller covering all its taxing jurisdictions, due no earlier than the twentieth day of the following month and rolling to the next business day on a weekend or holiday (or matching a remittance delayed by a Federal Reserve closure). It must make the Simplified Electronic Return available to every seller registered in the state, in the Governing Board's form, in two parts (remittances and allocations, and exempt sales). CSPs file the SER monthly in every member state where their Model 1 sellers are registered, plus the Article V audit reports; Model 2 and Model 3 sellers file part 1 monthly in every state where registered and part 2 either monthly or with the December return covering the year; Model 4 sellers may file the SER, part 1 monthly unless the state allows less often, and part 2 on the same options where they have a legal requirement to register, otherwise using the state's normal returns; part 2 can be demanded only by a state that notified the Governing Board, never from a Model 4 seller with no legal requirement to register there. A state may require three months' notice before a seller stops filing the SER. States must accept returns through the web services transmission, including multiple affiliated entities and multiple sellers in one transmission with no manual entry (by 1 January 2019), and must give a volunteer seller without a legal requirement to register notice and at least thirty days to file before assessing tax based only on a missed return, unless the seller has a history of non-filing or late filing.