Retailers participating in Massachusetts trade shows must register for a sales tax permit, collect sales tax on all taxable transactions during the event, and remit the collected taxes to the Massachusetts Department of Revenue via MassTaxConnect. They must also file sales tax returns even if no tax was collected, maintain detailed sales records, verify eligibility for exemptions, and ensure clear communication of tax obligations to customers. Proper compliance helps avoid penalties and ensures adherence to state tax laws, facilitating smooth participation in trade shows while maintaining good standing with tax authorities.