What Is Sales Tax Nexus?

Nexus Is the First Question - Not the Only Question

A business generally begins a sales-tax review by asking where it has sufficient connection, or nexus. If nexus exists, the next questions include whether the product or service is taxable, which jurisdiction's rules apply, the correct rate, exemption documentation, filing frequency, and whether a marketplace facilitator is collecting on the seller's behalf.

Nexus rules are state-specific and can change. A threshold that applies in one state may be measured differently or not apply in another. Local home-rule jurisdictions can add another layer.

Physical Nexus

Physical presence can arise from more than a headquarters. Employees, remote workers, offices, stores, warehouses, inventory held by a fulfillment provider, equipment, installation, repair work, trade shows, contractors, or other in-state activity may create obligations.

A small amount of physical activity can matter even when the business is below an economic threshold. Businesses should map people, property, inventory, and service activity - not only customer billing addresses.

Economic Nexus After Wayfair

In South Dakota v. Wayfair, Inc., the U.S. Supreme Court rejected the rule that physical presence was always required for a state to impose sales-tax collection duties on a remote seller. States subsequently adopted economic-nexus laws using sales, transaction, or other thresholds.

Threshold calculations vary. States may count gross sales, retail sales, taxable sales, exempt sales, marketplace sales, or different measurement periods. Some rules look backward, some forward, and some require action shortly after the threshold is crossed. Never assume a universal $100,000 rule.

Marketplace Sales Do Not End the Analysis

Marketplace-facilitator laws may require a platform to collect tax on facilitated sales. The seller may still need to monitor nexus, register, report marketplace sales, collect on direct sales, maintain exemption records, and understand whether marketplace activity counts toward a threshold.

Reconcile platform reports to the books and sales-tax returns. Sales tax collected is generally a liability held for the taxing authority, not ordinary business revenue.

A Repeatable Nexus Review

Track sales by destination state and channel each month or quarter. Maintain a calendar of thresholds and lookback periods, document physical activity, classify products and services, validate exemption certificates, and assign responsibility for registrations and filings.

If the business discovers a missed obligation, pause before filing old returns at random. Quantify the exposure, confirm the facts, and evaluate available state procedures with a qualified sales-tax adviser.

Questions to Ask Before You Act

• What decision are we trying to make, and by when?

• Are the underlying books reconciled and current?

• Which federal, state, local, industry, or contractual rules apply?

• Who owns the next step, and what documentation should be retained?

How Balance Partners Can Help

Balance Partners, LLC helps U.S. small-business owners build reliable accounting processes, understand their financial information, and coordinate bookkeeping, tax, and advisory needs. The right scope depends on your records, entity, locations, systems, and goals.

Jenny Gao, CPA, EA

Founder of Balance Partners. Florida-licensed CPA and IRS Enrolled Agent with more than a decade of accounting and tax experience. Jenny writes and reviews every guide on this site. About Jenny

This article is general educational information for U.S. business owners and is not accounting, tax, legal, payroll or financial advice for your situation. Rules change and vary by entity, state and facts. Balance Partners, LLC does not provide audit, review or other attest services. Last reviewed July 17, 2026.