Sales & use tax
Track state thresholds; check product taxability (e.g., digital goods, clothing variations by state).
Marketplace facilitators
Platforms may collect/remit for you; retain platform reports to support filings.
Inventory & nexus
3PL or warehouse locations can create nexus; register before collecting tax.
Returns & reconciliations
Match marketplace statements to your GL; resolve under/over‑collections.
International considerations
VAT/GST obligations arise when selling abroad; consider localized tax tools.