Sales Tax Compliance Across Multiple States: What You Need to Know
Selling in multiple states means tracking economic nexus thresholds, registering in each state, and filing on time. Here's how to stay compliant without getting buried.
Bizee Editorial Staff
Editorial Team
Introduction
Multi-state sales tax compliance comes down to 3 things: figuring out where you have economic nexus, registering in those states, and filing on time. The 2018 South Dakota v. Wayfair Supreme Court decision changed the rules — you can now owe sales tax in states where you've never set foot, based purely on your sales volume.
What economic nexus means for your business
Economic nexus is the legal threshold that triggers a sales tax obligation in a state — even if you have no office, warehouse, or employees there. Before 2018, physical presence was the only trigger. The Wayfair ruling changed that. Now, 45 states and Washington D.C. have economic nexus laws that apply to out-of-state sellers.
Most states use $100,000 in annual sales or 200 transactions as their threshold — but there's no uniform federal standard, so the number varies. Once you cross a state's threshold, you're on the hook for collecting and remitting sales tax there. The threshold resets each calendar year, so a business that crossed it last year needs to check whether it crosses again this year.
Most e-commerce sellers are surprised by how quickly they hit thresholds in states they've never thought about. A few hundred orders to customers in a single state can be enough.
How to know when you need to register in a state
You need to register for sales tax in a state when your sales into that state cross its economic nexus threshold. That means tracking both your total revenue and your transaction count by state — not just overall. Waiting until the end of the year to check is one of the most common ways businesses end up behind.
Physical presence still creates nexus too. If you store inventory in a fulfillment center, have employees working remotely, or attend trade shows in a state, those activities can trigger an obligation independent of your sales volume.
Track sales by state monthly, not annually — thresholds can be crossed mid-year
Check both revenue and transaction count; some states use one, some use both
Inventory stored in a third-party warehouse (including Amazon FBA) can create physical nexus
Review your nexus exposure any time you expand to a new sales channel or fulfillment partner
How to register for sales tax in multiple states
Once you've identified where you have nexus, you need a sales tax permit in each of those states before you start collecting. Collecting without a permit — or collecting and not remitting — can mean back taxes, interest, and penalties. Registration is done through each state's department of revenue, and most states handle it online.
If you have nexus in multiple states at once, the Streamlined Sales and Use Tax Agreement (SST) lets you register in up to 24 member states through a single centralized system. It doesn't cover every state, but it cuts down the administrative work significantly for sellers with broad geographic reach.
Registration steps for each state
Go to the state's department of revenue website and find the sales tax registration section
Have your EIN, business address, and estimated monthly sales volume ready
Submit the application and wait for your permit number — most states issue it within a few days online
Set your collection start date to the date you received the permit, not the date you crossed the threshold
For 24 SST member states, use the centralized registration at streamlinedsalestax.org to register in all of them at once
Common mistakes in multi-state sales tax compliance
The most common mistakes aren't about misunderstanding the law — they're about not tracking the right data at the right time. Businesses that sell across state lines often discover they've had nexus for months before they realize it, which means they've been collecting nothing and owe back taxes on every sale in that period.
Not monitoring sales by state until year-end, when nexus may have been triggered months earlier
Assuming economic nexus only applies to large businesses — a few hundred transactions can cross a $100,000 threshold faster than expected
Applying the wrong tax rate because rates vary not just by state but by county and city
Missing filing deadlines after registering — most states require monthly, quarterly, or annual returns depending on your sales volume
Not accounting for product taxability differences — digital goods, clothing, and groceries are taxed differently across states
If you've already missed filings in a state, a Voluntary Disclosure Agreement (VDA) lets you come forward proactively. Most states offer reduced or waived penalties through VDAs for businesses that self-report before an audit. A tax professional can help you figure out whether a VDA makes sense for your situation.
How to stay on top of ongoing compliance
Staying compliant across multiple states isn't a one-time project — it's an ongoing process. Sales tax rates and rules change regularly due to state legislation, and new nexus thresholds can take effect mid-year. The Federation of Tax Administrators and the Multistate Tax Commission both publish updates on state-level changes.
For most growing businesses, the practical answer is automation. Sales tax software that integrates with your e-commerce platform can calculate rates at checkout, track nexus thresholds by state, and generate returns automatically. It doesn't replace a tax professional for complex situations, but it handles the volume work that makes multi-state compliance hard to manage manually.
Review your nexus exposure in every state at least quarterly
Subscribe to rate update notifications from each state's department of revenue, or use a tax platform that does it for you
Keep records of your sales by state for at least 4 years — most states' audit lookback periods fall in that range
Talk to a tax professional any time you expand to a new state, add a new product category, or change your fulfillment setup
FAQ
No — only in states where you have nexus. Nexus can be physical (an office, warehouse, or employees) or economic (crossing a state's sales or transaction threshold). Once you have nexus in a state, you need a permit before you start collecting sales tax there. States without a sales tax — like Oregon, Montana, New Hampshire, and Delaware — don't require registration at all.
It depends on where the buyer is located. Most states use destination-based sourcing, which means the tax rate is based on the buyer's address, not yours. So if you're in Texas and you sell to a customer in California, you collect California's rate — assuming you have nexus there. Rates vary by state and often by county and city within a state, which is why multi-state sellers typically use software to calculate the right rate at checkout.
The Streamlined Sales and Use Tax Agreement (SST) lets you register in up to 24 member states through a single online application at streamlinedsalestax.org. For states not in the SST, you register directly through each state's department of revenue website. Most states process online registrations within a few business days. Have your EIN and estimated monthly sales volume ready before you start.
It means tracking where you have nexus, registering in those states, collecting the right rate at the point of sale, and filing returns on each state's schedule — monthly, quarterly, or annually depending on your volume. There's no federal sales tax in the U.S., so every state runs its own system with its own rates, thresholds, and filing deadlines. Businesses with broad reach across the country typically use sales tax automation software to manage the volume.
It depends on the tax type. For sales tax, compliance means registering where you have nexus, collecting the right rate, and filing on time. For federal income tax, it means accurate recordkeeping and timely filings with the IRS. Local taxes — like city or county sales taxes — are usually collected as part of the state rate if you use destination-based sourcing. A tax professional can help you figure out which obligations apply to your specific business structure and where you sell.
