US Sales Tax Economic Nexus Checker: Which States to Register

Since 2018 every sales tax state has its own economic nexus threshold, and they keep changing (Illinois dropped its 200 order test on 1 January 2026). Crossing one quietly means owing tax you never collected. This checks a seller's numbers against every state at once.

Built for ecommerce sellers, Shopify and Amazon store tools, bookkeepers, accounting software and AI agents that run a store's back office. Every answer names the law and links the official government page it came from, so a person can check it in one click.

What it returns

• Check my sales against every state (mode: "check"): Checks which US states a remote seller (no office, staff or stock in the state) must register in to collect sales tax, from its sales into each state. Give sales_by_state with the dollar sales and number of transactions (orders) per state, the period those figures cover, and whether they include sales made through marketplaces such as Amazon or Etsy. Returns states where the seller is over the economic nexus threshold (must register), states close to it (80 percent or more), states under it, and for each the threshold, the measurement period the state uses, what sales count (gross, retail or taxable only), whether marketplace sales count, when registration must happen, and the state revenue department source. Unclear cases give the SAFE answer (treated as over) with what it depends on.
• List state thresholds (mode: "list"): Lists the economic nexus threshold of every US sales tax state (or one state) on a date: dollar and transaction thresholds, and/or logic, measurement period, what counts, marketplace rules, when to register and the official source. Also lists the states with no statewide sales tax.
• Threshold changes (mode: "upcoming"): Lists economic nexus threshold changes in a date window (for example states dropping the 200 transaction test), soonest first, with the old and new rule and source. Use a past from_date to see recent changes.

Answers that depend on something you did not say come back as the safe answer (the stricter rule) plus a depends_on note saying what would change it.

Example input

{
  "mode": "check",
  "sales_by_state": [
    {
      "state": "CA",
      "sales": 612000,
      "transactions": 3400
    },
    {
      "state": "TX",
      "sales": 180000,
      "transactions": 950
    },
    {
      "state": "NY",
      "sales": 520000,
      "transactions": 90
    },
    {
      "state": "IL",
      "sales": 140000,
      "transactions": 1600,
      "marketplace_sales": 60000
    }
  ],
  "period": "last_12_months"
}

Example output (shortened)

{
  "date": "2026-10-10",
  "verdict": "Register in 1 state: CA.",
  "must_register": [
    {
      "state": "CA",
      "name": "California",
      "your_figures": {
        "sales_counted": 612000,
        "transactions_counted": 3400,
        "period": "last_12_months"
      },
      "threshold": "$500,000 in sales",
      "percent_of_sales_threshold": 122,
      "percent_of_transaction_threshold": null,
      "measurement_period": "previous or current calendar year (crossing in either counts)",
      "source": "https://www.cdtfa.ca.gov/industry/wayfair.htm",
      "verified_on_primary_source": true,
      "result": "Over the threshold on the figures given (SAFE answer): register to collect sales tax.",
      "register_by": "Register and start collecting straight after the sale that takes total sales over $500,000 (CDTFA example: threshold passed on 6 July, registration required on 7 July; the crossing sale itself is not taxed).",
      "register_by_date_if_crossed_today": "2026-10-10"
    }
  ],
  "close_to_threshold": [
    {
      "state": "NY",
      "name": "New York",
      "your_figures": {
        "sales_counted": 520000,
        "transactions_counted": 90,
        "period": "last_12_months"
      },
      "threshold": "$500,000 in sales and 100 transactions",
      "percent_of_sales_threshold": 104,
      "percent_of_transaction_threshold": 90,
      "measurement_period": "the 12 months (four quarters) ending with the last completed quarter",
      "source": "https://www.tax.ny.gov/pubs_and_bulls/publications/sales/nexus.htm",
      "verified_on_primary_source": true,
      "result": "Under the threshold but close (80 percent or more). Watch this state."
    },
    {
      "state": "IL",
      "name": "Illinois",
      "your_figures": {
        "sales_counted": 80000,
        "transactions_counted": 1600,
        "period": "last_12_months"
      },
      "threshold": "$100,000 in sales",
      "percent_of_sales_threshold": 80,
      "percent_of_transaction_threshold": null,
      "measurement_period": "the 12 months (four quarters) ending with the last completed quarter",
      "source": "https://tax.illinois.gov/research/publications/bulletins/fy-2026-12.html",
      "verified_on_primary_source": true,
      "result": "Under the threshold but close (80 percent or more). Watch this state."
    }
  ],
  "under_threshold": [
    {
      "state": "TX",
      "name": "Texas",
      "your_figures": {
        "sales_counted": 180000,
        "transactions_counted": 950,
        "period": "last_12_months"
      },
      "threshold": "$500,000 in sales",
      "percent_of_sales_threshold": 36,
      "percent_of_transaction_threshold": null,
      "measurement_period": "any rolling 12 month period",
      "source": "https://comptroller.texas.gov/taxes/sales/remote-sellers.php",
      "verified_on_primary_source": true,
      "result": "Under the threshold."
    }
  ],
  "data_as_of": "2026-10-10"
}

Inputs

• sales_by_state: One item per state the seller ships into: {"state":"CA","sales":612000,"transactions":3400}. Optional per item: marketplace_sales and marketplace_transactions (the part made through marketplace facilitators like Amazon), retail_sales (sales excluding sales for resale), taxable_sales (sales excluding exempt sales). Dollars are US dollars.
• period: What period the figures cover: last_12_months (default), previous_calendar_year or current_calendar_year (year to date).
• includes_marketplace_sales: True (default) if the sales and transactions figures include sales made through marketplace facilitators. Many states exclude those sales when testing a remote seller's threshold.
• date: The date to check the rules on, YYYY-MM-DD. Defaults to today. Thresholds changed in several states; past dates use the rule then in force.
• show_all_states: True to also list every sales tax state the seller did not report sales for. Default false.
• lookups: many questions in one run (up to 1,000), each item with the fields above.

Pricing

$0.003 per answered lookup (a listing mode is one lookup). Failed lookups (for example an address the US Census geocoder cannot find) are not charged. 1,000 lookups cost $3 US dollars.

For AI agents

• Runs through Apify's MCP server (https://mcp.apify.com/?tools=nerolabs/us-sales-tax-nexus) and through x402, so an agent without an Apify account can pay per call.
• A free MCP server with the same rules is at https://us-sales-tax-nexus.nerolabs.workers.dev/mcp for chat use; this actor adds bulk runs, datasets, scheduling, webhooks and Apify billing.
• Part of Nero Labs Rules: tools that answer rules which change after a model's training cutoff. The others: US minimum wage, pay transparency, US sales tax nexus, data breach deadlines.

Data and limits

• Built from primary sources only (statutes, regulators, revenue departments, official gazettes), each figure with its source URL and a verified_on_primary_source flag.
• Rules data is checked and updated by Nero Labs; every answer carries data_as_of.
• Information, not legal or tax advice. Check the linked source before acting on a close call.