Sales tax is one of the fastest ways an Amazon FBA seller or Shopify store owner ends up with an unexpected liability. You can cross an economic nexus threshold (the sales volume that legally requires you to collect and remit tax in a state) without ever receiving a notice. By the time a state contacts you, back taxes, interest, and penalties are already stacking up.
Most eCommerce sellers are not ignoring sales tax on purpose. At AMZ Accountant, we find they often lack a clear process to track where they owe and when deadlines hit across multiple states. A working sales tax compliance checklist solves this by providing a repeatable system instead of a recurring fire drill.
Keep reading to learn exactly how to build that system, from confirming nexus and registering permits to collecting the right data and filing on time. By the end of this guide, you will know which steps to take first, which mistakes cost sellers the most money, and when it makes sense to bring in a specialist.
Know Where You Owe Tax
Knowing where you have tax obligations is the first thing to lock down, because registering in the wrong states (or missing the right ones) is the single biggest compliance gap for online sellers.
Economic Nexus Thresholds
After the 2018 South Dakota v. Wayfair Supreme Court decision, states can require you to collect sales tax based on your revenue or transaction volume alone. You do not need a warehouse or office in a state to owe tax there.
Most states set the economic nexus threshold at $100,000 in sales or 200 transactions per year. Some states are stricter. California triggers nexus at $500,000 in annual sales. A few states have no transaction count threshold at all and rely on revenue only.
You need to track your gross sales by state every month. Use tax automation software to pull Amazon sales data by state, then map it against each state’s threshold. When you approach 80% of a threshold, that is your cue to start the registration process, not wait until you have crossed it.
| State | Revenue Threshold | Transaction Threshold |
| California | $500,000 | None |
| Texas | $500,000 | None |
| New York | $500,000 | 100 transactions |
| Most other states | $100,000 | 200 transactions |
| Missouri | $100,000 | None |
Marketplace Facilitator Rules
Amazon collects and remits sales tax on your behalf in all 50 states for sales made through their marketplace. This is because Amazon qualifies as a marketplace facilitator under state law.
That does not mean you have zero filing obligations. If you also sell on your own Shopify store, through your website, or at in-person events, those sales are your responsibility. You collect the tax, you file the return, you remit the money. Assuming Amazon covers everything is one of the most common mistakes multi-channel sellers make.
- Amazon: collects and remits in all 50 states as a marketplace facilitator
- Walmart Marketplace: collects and remits in most states
- Etsy: collects and remits in most states
- eBay: collects and remits in most states
- Shopify store (your own domain): your responsibility entirely
- Your own website or app: your responsibility entirely
Physical Presence Triggers
Even with marketplace facilitator rules handling Amazon sales, physical presence still creates nexus in states where you have inventory. If Amazon stores your FBA inventory in a Pennsylvania fulfillment center, you likely have nexus in Pennsylvania.
Other physical presence triggers include: employees working remotely in a state, contractors fulfilling orders, trade show attendance, and pop-up retail events. A third-party logistics (3PL) warehouse also counts as a physical presence trigger in most states.
Review your FBA inventory distribution report in Seller Central at least quarterly. Once you know which states hold your inventory, you know your minimum nexus footprint, regardless of revenue thresholds. Once you know where you owe, the next step is confirming whether what you sell is actually taxable in those states.
Confirm What Your Products Require
Not every product you sell is taxable in every state, and getting this wrong leads to either under-collecting (your liability) or over-collecting (a customer service problem that also signals compliance gaps).
Taxability by Product Type
Physical goods are taxable in most states, but exemptions vary widely. Clothing is exempt in Pennsylvania and New Jersey but taxable in most other states. Groceries are partially or fully exempt in many states. Supplements, vitamins, and health products vary by state, sometimes taxed as general merchandise and sometimes exempt as food or medicine.
Digital products are taxable in about half of U.S. states. If you sell digital downloads, software, or online courses, you need to check each state’s rules individually. This is a common gap for Shopify sellers who bundle physical and digital goods.
Exemptions and Resale Certificates
If you purchase inventory to resell, you should not be paying sales tax on those purchases. A resale certificate (also called a reseller permit) allows you to buy products tax-free for resale.
Each state issues its own resale certificate. If you buy inventory from a supplier in multiple states, you need a certificate for each state. Keep these on file. Auditors look for them first.
Resale certificate checklist:
- Obtain your permit from each state where you purchase goods for resale
- Provide the certificate to your supplier before the purchase, not after
- Update the certificate whenever your business information changes
- Store copies in your document management system, ideally your QuickBooks Online or portal files
State-by-State Rule Differences
There is no federal sales tax standard. Each state writes its own rules. What is taxable in Ohio may be exempt in Colorado. Product taxability research is not a one-time task. States regularly update tax rates, exemptions, nexus requirements, and product taxability rules.
Keeping up with these changes is a major challenge for online sellers. Thousands of state and local tax jurisdictions across the United States can change rates and rules throughout the year, and many states introduce new taxability requirements for digital products, services, and marketplace sales.
If you are manually tracking taxability, you are already at a disadvantage. Automated sales tax software can help monitor rate and rule changes across jurisdictions, while a CPA with eCommerce tax expertise can help ensure your products are classified correctly. Once you know what is taxable and where, you are ready to register and legally start collecting sales tax.
Set Up Registration Before You Collect
Collecting sales tax without a valid permit is illegal in most states. Registration comes before collection, not after.
Sales Tax Permit Applications
You register for a sales tax permit through each state’s revenue department website. Most states process applications online. Common information you will need includes your federal EIN (Employer Identification Number), legal business name, business address, and the start date of your nexus in that state.
Some states charge a small registration fee. Others are free. Processing times range from same-day (common in most states) to several weeks for states with manual review processes. Start early so you do not collect tax without a valid permit.
Effective Dates and Filing Frequencies
When you register, the state will assign you an effective date and a filing frequency. Your filing frequency is usually tied to your expected sales volume in that state:
| Expected Annual Tax Collected | Typical Filing Frequency |
| Under $1,200 | Annual |
| $1,200 to $12,000 | Quarterly |
| Over $12,000 | Monthly |
Your effective date matters because you cannot collect and remit tax for periods before it. If you registered late and have back liability, it is handled through voluntary disclosure, a separate process that lets you come clean with limited penalty exposure.
Channel and Entity Alignment
Make sure your permits list the correct legal entity. If your Shopify store operates under a DBA or a different LLC than your Amazon FBA business, you may need separate permits. Mismatches between the entity on your permit and the entity on your tax return are a common audit trigger.
Also confirm that your sales channels are correctly configured to collect tax only in states where you have a valid, active permit. Collecting in a state where you are not registered creates its own compliance problem.
With your permits in place, the next step is to ensure your checkout and data systems collect and store the right information for every sale.
Build a Reliable Collection and Recordkeeping Process
Your registration is active, your permits are filed, now you need clean data flowing through your checkout and accounting tools every single day.
Checkout Tax Settings
On Shopify, go into your tax settings and enable collection for each state where you hold a permit. Shopify calculates rates automatically based on the customer’s shipping address. Review these settings whenever you register in a new state or when a state updates its rates.
For Amazon FBA, Amazon handles collection on your marketplace sales. Your job is to ensure your A2X account pulls accurate state-level sales data and syncs it to QuickBooks Online correctly, so your records match what Amazon remitted on your behalf.
Marketplace and Website Data Reconciliation
When you file a return for a state where Amazon also remits on your behalf, your gross sales figure includes both Amazon-remitted and Shopify-collected amounts. Filing only your Shopify portion correctly requires reconciling the two data sources every month.
A2X pulls Amazon settlement data and categorizes it by state, fee type, and transaction type. Map those categories to matching accounts in QuickBooks Online, so your monthly reports show what you collected, what Amazon remitted for you, and what you still owe. This reconciliation step prevents both under-filing and over-filing.
Monthly reconciliation checklist:
- Pull A2X sales summary by state for the month
- Match Amazon-remitted tax to your Shopify-collected tax by state
- Confirm gross sales figures match your platform dashboards
- Flag any state where collections differ from prior months by more than 10%
- Export and store final reconciled reports in your client portal or document folder
Document Retention Standards
Most states require you to keep sales tax records for at least three years. Some states, including California and New York, can audit up to four years back. A few states have no statute of limitations if fraud is suspected.
Keep: filed returns, payment confirmations, resale certificates, exemption certificates, monthly reconciliation reports, and A2X exports. Store them in a secure, cloud-based location with version control. Your QuickBooks Online file should match every return you file.
With clean records in place, your filing and remittance process becomes straightforward rather than stressful.
File Returns and Remit on Time
Late filing and late payment are the two most common ways eCommerce sellers accumulate penalties, and both are entirely avoidable with a calendar and a process.
Monthly, Quarterly, and Annual Deadlines
Most states set filing deadlines on the 20th of the month following the reporting period. Some states use the last day of the month. A handful use the 25th. There is no single national rule, so you need a deadline calendar specific to your active states.
If you are filing in 10 or more states, managing deadlines manually is a real risk. A missed filing in California, for example, can trigger a 10% late penalty plus interest. In Texas, the penalty is 5% for the first 30 days, then 10% after that.
Zero Returns and No-Sales Periods
Even if you made no taxable sales in a state during a reporting period, you may still be required to file a zero return. Failing to file a zero return is treated the same as failing to file a regular return in most states.
This catches many Amazon sellers off guard. If your FBA inventory leaves a state’s fulfillment centers and you stop selling there, your nexus and filing obligations may remain active until you formally close your permit with the state.
Penalty Prevention Steps
Steps to avoid late penalties:
- Build a filing calendar that lists every state, its due date, and the reporting period covered
- Set a reminder 10 days before each deadline to finalize your reconciliation
- Confirm payment was processed and note the confirmation number in your records
- For annual filers, schedule a quarterly check-in to make sure your volume has not pushed you into a higher frequency tier
- If you miss a deadline, file as soon as possible to stop penalty accumulation
Your collection and filing process needs to evolve as your business grows, because more revenue often means new states and new obligations.
Review the Checklist as You Scale
A compliance checklist is not a one-time setup. It needs a quarterly review, especially when your sales are growing or your channel mix is changing.
New States and New Channels
Every time your sales in a new state approach $80,000 or 160 transactions, add that state to your registration pipeline. Do not wait for the threshold to pass. Registration takes time, and you want your permit active before you begin collecting.
Adding a new sales channel, like listing on Walmart Marketplace or launching a B2B wholesale site, changes your nexus analysis. Walmart remits on your behalf as a marketplace facilitator, but a wholesale channel in which you invoice business customers directly places the collection and filing obligations back on you.
International Expansion Into the U.S.
If you are a foreign business entering the U.S. market, your sales tax obligations begin as soon as you create nexus in any U.S. state. Storing inventory in a U.S. fulfillment center, even through Amazon FBA, creates physical nexus.
Your home country’s VAT or GST rules do not apply here. U.S. sales tax is administered by the states, and each state has its own registration, collection, and remittance requirements.
The entity structure you choose for your U.S. business also affects your filing obligations. An LLC taxed as a sole proprietor and a C-corp have different reporting requirements at both the state and federal level. Getting the structure right from the start avoids costly corrections later.
When to Get Expert Support
If you are managing nexus in five or more states, running both Amazon and Shopify, or approaching seven figures in revenue, your sales tax exposure is significant enough to warrant professional oversight.
A CPA who specializes in eCommerce accounting can catch threshold crossings before they become liabilities, handle voluntary disclosure when needed, and keep your filing calendar current as state rules change.
You can learn about sales tax nexus compliance for Shopify sellers and Amazon FBA businesses to see what a structured compliance review looks like from a licensed CPA’s perspective.
Frequently Asked Questions
When Does an Amazon or Shopify Seller Trigger Sales Tax Nexus?
Nexus (the legal connection to a state that requires you to register and collect sales tax) is triggered two ways: economic activity or physical presence. Economic nexus kicks in when you cross a state’s revenue or transaction threshold, usually $100,000 or 200 transactions per year. Physical nexus is triggered the moment your inventory, employees, or contractors are located in a state.
What Numbers Do I Need to Track Each Month to Stay Ahead of Economic Nexus Thresholds by State?
Track gross sales revenue and order count by state every month. Use A2X to pull this data from your Amazon settlements and Shopify payouts, then export it to a simple state-by-state tracker. Flag any state where you have crossed 70% of the applicable threshold, so you have time to register before you are legally required to collect.
How Do I Confirm Which States My Marketplace Collects and Remits for Me, and Where I Still Have Filing Exposure?
Amazon, Walmart, Etsy, and eBay all collect and remit sales tax as marketplace facilitators in most U.S. states. Your exposure comes from channels outside those platforms, specifically your own Shopify store, your website, or any direct B2B invoicing. Review your sales channel list and identify every channel that is not a marketplace facilitator, then confirm the registration and collection status for each.
What Documents Should I Keep to Support Exempt Sales and Resale Certificates During a Sales Tax Audit?
Keep a copy of every resale or exemption certificate you have issued or accepted, the original purchase orders or invoices those certificates cover, and documentation showing the buyer was eligible for the exemption. Store these in a cloud-based system alongside your filed returns. Most states require you to retain these records for at least three to four years.
How Do I Reconcile Sales Tax Collected to Filed Returns When Amazon Settlements and Shopify Payouts Do Not Match Cleanly?
Use A2X to separate Amazon settlement data into gross sales, fees, refunds, and tax collected by state. Sync that data to QuickBooks Online so each component has its own account category. Your Shopify tax reports should show gross sales and tax collected by state separately. Reconcile both sources to your filed return totals every month before you submit a return, not after.
What Is the Fastest Way to Catch Up on Past-Due Sales Tax Filings Without Creating New Penalties or Audit Risk?
Voluntary disclosure agreements (VDAs) let you come forward proactively in most states and settle back tax liability with limited lookback periods and reduced or waived penalties. You typically need to disclose before the state contacts you for the agreement to apply. Work with a CPA who has experience negotiating VDAs for eCommerce businesses to minimize your exposure and get compliant without triggering a full audit.
Your Next Step Is Simpler Than You Think
Sales tax compliance for Amazon sellers and Shopify store owners is not simple, but it is manageable when you follow a structured process. Know where your nexus is, confirm what your products require, register before you collect, keep clean records, and file on time. Revisit the checklist every quarter as your revenue and channel mix grow.
The sellers who get into trouble are not the ones who misunderstood the rules. They are the ones who put the checklist off until a deadline passed or a state sent a notice. A proactive approach now costs far less than a reactive one later.
If your books are not built for eCommerce, your tax bill is probably higher than it should be. Schedule a free consultation with AMZ Accountant and find out exactly where your sales tax exposure is and how much you could save this year.