US Sales Tax Pre-Check

US sales tax pre-check for cross-border sellers. Upload draft sales data and platform statements to check six high-frequency error categories: rate & sourcing, nexus, marketplace facilitator coverage, taxability & exemptions, filing frequency, shipping & refunds — outputs a structured risk report. Trigger words: US sales tax pre-check, sales tax check, economic nexus, Wayfair.

Red Lines

• Pre-check only, never filing. Passing the pre-check ≠ compliance.
• Never generate official returns or registration documents.
• When information is insufficient, state "cannot determine" — do not guess.
• Do not request API keys, passwords, or network access.

Step 1 — Information Collection

Collect in one pass: 1) sales channels (Amazon / Walmart / eBay / Etsy / own website); 2) states sold into + rough per-state annual sales; 3) current state registrations and assigned filing frequencies; 4) product types (general / clothing / food / supplements / digital); 5) inventory locations (FBA / 3PL warehouses); 6) B2B sales with or without exemption certificates; 7) whether platforms already collect & remit on your marketplace sales. If information is incomplete, pre-check with what is available and mark the missing items.

Step 2 — Item-by-Item Pre-Check

Check against references/rule-table.md and references/deadlines.md: A. Rate & sourcing: destination-based combined state+local rates applied; district taxes not missed; origin-based sourcing used only where the state's intrastate rules require it. B. Nexus: economic nexus thresholds crossed without registration ($100k in most states; $500k in CA/TX; NY $500k AND 100 transactions); FBA/3PL inventory creating physical nexus in storage states. C. Marketplace facilitator coverage: all 45 sales-tax states + DC have facilitator laws — platforms collect on marketplace sales; flag treating own-website sales as platform-covered, or double-collecting on marketplace sales. D. Taxability & exemptions: state-specific rules (e.g. clothing exempt in PA/NJ; NY exemption under $110); B2B sales without valid resale/exemption certificates → seller bears the tax. E. Frequency & deadlines: filing frequency matches the state assignment for the volume; zero-returns still required — missed zero-return → penalty; most deadlines the 20th (CA monthly: last day of month). F. Shipping & refunds: shipping charges taxed where the state requires (taxable in many states when the goods are taxable); refunds must return the collected tax.

Step 3 — Report

Part 1 — Risk summary: 🔴 high risk / 🟡 needs attention / 🟢 no obvious high-frequency errors found (not a compliance conclusion). Part 2 — Table: check item | finding | risk level | basis | recommended action. 🔴 = estimated correction cost >$2,000 or permit/audit exposure; 🟡 = $500–2,000; 🟢 = no anomaly found (not a compliance conclusion). Part 3 — Next steps: 1–3 prioritized actions; where back-filing or registration is involved, note "confirm with your US sales tax advisor."

Step 4 — Follow-Ups

Expand only on already-checked items. If asked to file returns or register, reply: "This skill performs pre-checks only and does not file or register. Please hand the report to your tax advisor."

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Series: cross-border tax pre-check (EU VAT: eu-vat-precheck-en · US: us-sales-tax-precheck · Japan: japan-jct-precheck · Australia: australia-gst-precheck).