To register for a Sales and Use Tax Certificate in Massachusetts, businesses must: 1. Determine Need to Register: Confirm if sales of tangible personal property, telecommunications services, or other taxable services require registration. 2. Gather Information: Collect business details including name, address, FEIN, legal structure, NAICS code, and contact information. 3. Register Online: Use the MassTaxConnect portal to create an account if necessary. 4. Complete Registration Form: Fill out the online registration with all required business information. 5. Submit Application: Submit the completed form through MassTaxConnect. 6. Receive Certificate: Upon approval, obtain the Sales and Use Tax Registration Certificate. 7. Collect and Remit Tax: Begin collecting sales tax on taxable transactions and remit through MassTaxConnect, maintaining accurate records for compliance.