State Sales Tax — Quarterly Overview

Who must file or pay

Businesses that sell taxable goods or certain services, with nexus in any state that has a sales tax. Economic nexus thresholds (post-Wayfair) typically apply once you exceed $100,000 in sales or 200 transactions in a state.

What you need to know

Sales tax obligations are determined by state law and vary significantly. After the Supreme Court's 2018 Wayfair decision, every state with a sales tax can impose "economic nexus" — meaning you can owe sales tax in a state where you have never set foot, purely based on online sales volume.

Most states require quarterly filing for moderate-volume sellers, with due dates falling on the last day of the month following the quarter: April 30, July 31, October 31, and January 31. High-volume sellers are often required to file monthly.

If you sell physical products online (Shopify, Amazon, eBay, Etsy), you likely have sales tax obligations in multiple states you may not be aware of. TaxosAgent's business services tier includes a nexus review and registration support as part of entity formation and bookkeeping.

Penalties vary by state. Most states charge 5%–10% of unpaid tax per month. California charges 10% plus interest. Willful failure to collect or remit can result in personal liability for sales tax, similar to the federal Trust Fund Recovery Penalty.

Required forms

• →State sales tax return (form varies by state)
• →Form ST-1 (CA), ST-809 (NY), etc.

Go deeper

A licensed TaxosAgent professional reviews your situation before this deadline — so you maximize savings, not just compliance.