Marketplace seller compliance package

I completed targeted research to gather authoritative, up-to-date sources needed to create a comprehensive blog post and newsletter titled "Marketplace seller compliance package" for US business owners and LLC founders. The research focused on marketplace facilitator laws, state economic nexus thresholds and registration requirements, marketplace platform collection/remittance responsibilities, 1099-K reporting changes, practical compliance checklists (registration, resale certificates, recordkeeping, bookkeeping, automation), and sample state-specific notes for key states. I collected and compressed content from federal and state tax authorities, tax research organizations, and major marketplace/platform guidance pages. The findings and source excerpts below include the key legal rules, effective dates, thresholds, registration guidance, and recordkeeping/notification practices you will need to develop the blog and newsletter content.