IRS Sales Tax Nexus Crackdown Hits Multistate Sellers Hard in 2026

A wave of multistate sales tax audits is landing on ecommerce operators’ desks this spring, and the timing couldn’t be worse. With Q2 inventory builds already straining cash flow, hundreds of Shopify and Amazon sellers are receiving nexus determination letters from state revenue departments — several of which have signed new data-sharing agreements with the IRS as part of a coordinated enforcement push that began in January 2026.

According to compliance platform Avalara, the number of nexus-related audit inquiries processed through its system jumped 41% year-over-year in Q1 2026, with the sharpest spikes hitting sellers operating in Texas, Pennsylvania, and Colorado — three states that finalized upgraded data-access protocols with federal authorities in late 2025. TaxJar, now fully integrated into Stripe’s financial infrastructure, reported a similar uptick, with its merchant alert volume hitting a record high in April.

What triggered the 2026 sales tax enforcement surge?

The enforcement push traces back to two structural shifts. First, the IRS’s 1099-K reporting threshold dropped to $600 in aggregate annual transactions starting in tax year 2025, generating an enormous new dataset linking seller identities to marketplace gross merchandise volume. Second, states accelerated adoption of the Streamlined Sales and Use Tax Agreement (SSUTA), giving revenue departments standardized tools to cross-reference federal 1099-K filings against state tax registration records.

“What we’re seeing is the first generation of 1099-K data from the $600 threshold actually hitting state desks at scale,” said Liz Armbruster, head of indirect tax policy at Avalara, in a phone interview last week. “For sellers who’ve been operating in gray areas on economic nexus — say, $85,000 in Texas with no registration — that data is now in the hands of the Comptroller’s office.”

“Sellers who thought they were too small to audit are getting letters. The threshold for state attention has dropped significantly because the data quality has improved so dramatically.” — Liz Armbruster, Head of Indirect Tax Policy, Avalara

💡 Article Summary

Key Insights

1

What triggered the 2026 sales tax enforcement surge?

2

Which seller profiles are most exposed to nexus audit risk?

3

How are compliance platforms responding to the enforcement wave?

4

What should Shopify and Amazon sellers do right now?

5

Are marketplace facilitator laws providing sellers enough protection?

Source: Ecommerce Times

Economic nexus thresholds — established after the Supreme Court’s 2018 South Dakota v. Wayfair ruling — remain at $100,000 in sales or 200 transactions in most states. But enforcement of those thresholds was historically inconsistent. The new data pipelines are closing that gap fast.

Which seller profiles are most exposed to nexus audit risk?

Tax compliance attorneys say the highest-risk sellers share a common profile: they crossed economic nexus thresholds in multiple states between 2022 and 2024 during the post-pandemic volume surge, registered in none of them, and have since normalized to lower volumes — making them invisible to self-reporting triggers but still flagged in historical 1099-K data.

Michael Gilmore, a partner at Seattle-based ecommerce tax firm Peisner Johnson, has seen a spike in voluntary disclosure agreement (VDA) applications from clients since February. VDAs allow sellers to come forward proactively and typically cap lookback periods at three to four years while waiving penalties.

“The smart move right now is VDA before the letter arrives. Once you’re in audit, you lose leverage on penalty abatement and the lookback window often extends further. We’re filing more VDAs in Q1 2026 than in any full year prior.” — Michael Gilmore, Partner, Peisner Johnson

The at-risk seller profiles include:

• Amazon FBA sellers with inventory stored in fulfillment centers in states where they haven’t registered — physical presence nexus, not just economic nexus
• Shopify merchants who expanded to Walmart Marketplace or TikTok Shop in 2023-2024 and crossed thresholds on combined volume
• DTC brands that ran aggressive paid media campaigns into California, New York, and Illinois without modeling the resulting nexus exposure
• Wholesale-to-DTC pivots that changed their sales mix but didn’t reassess tax obligations under the new structure

How are compliance platforms responding to the enforcement wave?

The audit surge is accelerating adoption of automated tax compliance tools, but it’s also exposing gaps in legacy implementations. Several mid-market operators running Avalara’s older AvaTax configuration report that their nexus tracking wasn’t set up to flag Amazon FBA warehouse locations as physical presence triggers — a known configuration gap that Avalara addressed in a product update in March 2026.

TaxJar’s AutoFile product, which handles state return filing automatically once a seller registers, has seen subscription upgrades spike 38% since January, according to figures shared with Ecommerce Times. Stripe, which acquired TaxJar in 2021, pushed an updated nexus monitoring dashboard to all Stripe Tax users in April that surfaces real-time threshold proximity alerts by state.

Newer entrants are also gaining traction. Numeral, a compliance automation startup founded in 2022, closed a $14 million Series A in March and counts roughly 1,200 Shopify merchants as customers. The platform specializes in retroactive nexus analysis — pulling historical order data to map exactly when and where a seller crossed thresholds — which has become a core pre-VDA workflow.

“We’re running retroactive analyses for sellers going back to 2020,” said Barr Yaron, Numeral’s co-founder, in a written statement to Ecommerce Times. “Most are surprised by how many states they’ve had exposure in. The good news is that voluntary disclosure programs exist in nearly every state. The window to use them is closing as enforcement ramps up.”

What should Shopify and Amazon sellers do right now?

Tax compliance advisors and platform vendors are converging on a consistent set of immediate actions for sellers who haven’t done a formal nexus review in the past 12 months:

• Pull your 1099-K data by state from every marketplace — Amazon Seller Central, Shopify, Walmart, TikTok Shop — and map it against economic nexus thresholds for each state where you had transactions
• Cross-check FBA warehouse locations against your state registrations. Amazon’s inventory placement algorithm may have created physical nexus in states you didn’t anticipate. Amazon’s seller reports include the fulfillment center IDs; Avalara and TaxJar both offer tools to map those IDs to states
• Run a voluntary disclosure eligibility check for any state where you’ve exceeded thresholds without registration. Most states require no prior contact from the revenue department for VDA eligibility
• Audit your compliance platform configuration, not just your registration status. Incorrect product taxability settings or misconfigured nexus triggers are among the most common sources of under-remittance
• Model your 2026 exposure forward, particularly if you’re scaling into new channels. TikTok Shop and Whatnot are generating meaningful GMV for some sellers without built-in tax reporting infrastructure equivalent to Amazon’s

Are marketplace facilitator laws providing sellers enough protection?

A common misconception among newer sellers is that marketplace facilitator laws — which require platforms like Amazon and Shopify to collect and remit sales tax on behalf of sellers in most states — eliminate their compliance obligations entirely. They don’t.

Marketplace facilitator laws cover the sales tax on transactions processed through the platform, but they don’t eliminate a seller’s registration obligations in states where they have nexus, don’t cover income tax obligations that may arise from business activity in a state, and don’t apply to direct-to-consumer sales made through a seller’s own Shopify storefront where the seller is the merchant of record.

“There’s a meaningful segment of mid-market DTC operators running both an Amazon channel and a direct Shopify channel,” said Armbruster of Avalara. “Amazon handles the tax on the Amazon side. Nobody’s handling it on the Shopify side if the seller hasn’t set up Avalara or TaxJar correctly. That gap is where we see the biggest exposure.”

“Marketplace facilitator protection is real but narrow. Sellers with omnichannel operations can’t assume they’re covered. The Shopify channel is almost always the liability gap.” — Liz Armbruster, Head of Indirect Tax Policy, Avalara

What does the enforcement trend mean for 3PLs and fulfillment networks?

The nexus crackdown has a secondary operational implication that’s beginning to surface in conversations between merchants and their 3PL partners: inventory placement decisions now carry explicit tax consequences.

Distributed inventory models — popularized by ShipBob, Flexport’s fulfillment arm, and Amazon’s own inventory placement algorithm — spread stock across multiple warehouse nodes to reduce shipping zones and delivery times. Each node in a new state can create physical presence nexus.

Several larger Shopify merchants are now requiring 3PLs to disclose the full list of states in which their warehouses operate during contract negotiations, and some are structuring inventory placement to deliberately avoid certain high-audit-risk states until their compliance infrastructure is in place. ShipBob confirmed to Ecommerce Times that it added a nexus disclosure section to its standard merchant onboarding documentation in Q1 2026 following merchant requests.

For DTC operators scaling into new fulfillment relationships this summer, the operational calculus around warehouse placement has meaningfully changed. The cheapest shipping zone optimization is no longer necessarily the right answer if it creates a six-figure retroactive tax liability in a state where enforcement is accelerating.

Tax compliance, long treated as a back-office afterthought by growth-focused ecommerce teams, is forcing its way into supply chain strategy meetings. The sellers who adapt fastest will be the ones who treat nexus mapping as infrastructure — not cleanup.