E-commerce tax compliance service

I performed a targeted web search and extraction to gather up-to-date, authoritative resources (state guides, tax software vendors, tax research firms and expert commentary) on e-commerce sales/use tax compliance for U.S. businesses.

The research focused on: economic nexus rules and thresholds, marketplace facilitator laws, state registration and filing steps, commonly counted/excluded transactions and exemptions, penalties/audits, and recommended automation tools and workflows.

Using those sources I summarized the essential compliance points and produced a consolidated checklist and guidance a US business owner/LLC founder can follow to build an e-commerce tax compliance service or internal process.

Key findings and practical guidance are below.Summary of key findings (concise):- Economic nexus: States commonly use dollar-sales thresholds (most often $100,000) and/or transaction-count thresholds (historically 200 transactions) to trigger remote seller registration, collection and remittance obligations.

States differ on which sales count toward thresholds (taxable goods, some services, marketplace sales, exempt sales in some cases) and on the evaluation period (prior calendar year, preceding 12 months, quarter-to-quarter).- Transaction thresholds changing: Several states removed the 200-transaction threshold in 2025, and additional removals (e.g., Illinois on Jan 1, 2026) are effective meaning more sellers will reach nexus based only on dollar thresholds.

Track state-by-state updates annually.- Marketplace facilitator laws: Most states have marketplace facilitator laws that require the marketplace (e.g., Amazon, Etsy) to collect and remit tax in many cases.

However, rules vary by state about whether marketplace-facilitated sales count toward the sellers economic nexus threshold and whether the facilitator relieves the seller of collection obligations you must verify each states rule.- Registration and filings: Once nexus exists, register with that states Department of Revenue, collect the appropriate tax (rate depends on destination-based sourcing and product taxability), remit collections on the states schedule, and file returns.

Filing frequencies and form requirements vary by state.- Product taxability & exemptions: Not all products/services are taxable. Maintain accurate product tax codes, collect and store resale/exemption certificates, and use exemption-certificate management.

Exempt/for-resale sales may or may not count toward nexus thresholds depending on state.- Penalties & audits: Noncompliance can trigger back liability, penalties, and audits. Some states require retroactive registration and remittance when nexus is found; remedial options vary.- Automation & vendors: Leading tax automation and managed services (Avalara/AvaTax, TaxJar, Sovos, Vertex, Stripe Tax, AVASK and others) can automate calculation, nexus tracking, registration, returns and exemption certificate management.

For many sellers, automation plus periodic tax advisor review is the recommended model.Practical compliance checklist / action plan for US e-commerce businesses (LLC founders):

Inventory & sales mapping

Map product catalog and sales channels by destination state and product taxability. Tag products with appropriate tax codes.

Nexus monitoring

Continuously monitor sales and transaction counts by state on a rolling basis (prior 12 months / state-specific rule). Use automation tools for near-real-time monitoring.

Marketplace rules

For sales through marketplaces, confirm facilitator collection rules and whether marketplace sales count toward your nexus thresholds in each state.

Register timely

When a threshold is crossed, register promptly with the states revenue department to avoid penalties (follow each states registration process).

Start collecting

Configure your checkout to collect the correct tax rates (state, county, city, special district) and product taxability rules.

File & remit

Maintain a calendar of state filing deadlines and frequencies; use software or a managed filing service to submit returns and remit payments.

Exemption management

Collect, validate and store resale/exemption certificates (use tools like CertCapture or equivalent).

Reconcile & audit readiness

Reconcile collected tax to remittances and maintain supporting documentation (sales detail, nexus analyses, exemption certificates) for at least the maximum state statute-of-limitations period.

Consider retroactive exposure

If nexus existed previously but you failed to register, consult a tax advisor some states offer voluntary disclosure programs to limit penalties.

Use automation + advisor

Combine a robust tax engine (AvaTax, TaxJar, etc.) with periodic expert review to handle rule exceptions and complex taxability.