Simplified QuickBooks Accounting for Shopify & Amazon Sellers
Sales Tax Services
US Sales Tax Compliance and Canadian GST/HST Services for Amazon FBA and Shopify Sellers
Whether you’re navigating the US economic nexus for the first time, registering for Canadian GST/HST, cleaning up years of back filings, or facing an audit, Thelonex provides complete sales tax management for e-commerce sellers in the US and Canada.
Sales Tax is Confusing, But Also Costly When Ignored
If any of these sound familiar, you're in the right place.
I don't know where I'm supposed to collect sales tax
I'm not sure if I have nexus in a state
I've made sales but never registered
I'm behind on filings and don't know how to catch up
I'm being audited and have no idea how to handle it
I sell into Canada but have no idea about GST/HST or provincial tax obligations
Sales takes too much time and I don't know who to trust with it
Sales tax is the most penalized compliance area for e-commerce sellers — yet it's the most ignored. States don't send warnings before they send audit notices. The Wayfair decision changed everything in 2018, and most sellers still haven't caught up. The good news: there are legal programs to come forward voluntarily, limit your liability, and get compliant before you're forced to.
Sales Tax Services That Solve Real Problems
Sales tax non-compliance is more common than you think — and far more fixable than most sellers fear. Whether you've been collecting but not filing, selling across states without registering, or completely unaware of your Canadian GST/HST obligations, we've handled situations exactly like yours. We assess your exposure, map your obligations, and build a clear compliance plan — for both the US and Canada — so you know exactly where you stand and exactly what it costs to fix.
Your Complete Ecommerce Accounting Partner
Rather than hiring different vendors for each service, we can take care of it all under one roof.
Ecommerce Accounting
Clean monthly P&L, Balance Sheet, and cash flow reports — reconciled across Amazon and Shopify in QuickBooks Online, delivered by the 5th of every month.
Learn More →QuickBooks Setup
Get your QBO configured correctly for e-commerce from day one — with A2X integration, e-commerce chart of accounts, and sales tax settings properly configured.
Learn More →Catch-Up Services
Behind on your books? We clean up months or years of backlog in QuickBooks Online and deliver a tax-ready package your CPA can use.
Learn More →Why Thelonex
⚖️ VDA & CRA VDP Specialists Voluntary Disclosure Agreements in the US and CRA Voluntary Disclosure Program applications in Canada are not standard accounting work — they require specialist knowledge of each state’s and the CRA’s specific procedures. We handle these regularly for e-commerce sellers.
🔍 Amazon FBA Nexus Experts We understand how Amazon’s FBA network creates physical presence nexus across multiple states — and how that interacts with economic nexus thresholds. Most general accountants don’t. We do.
🇨🇦 Canada-Literate on Both Federal and Provincial Tax GST/HST is federal. QST is Quebec-administered. PST varies by province. BC, Saskatchewan, Manitoba, and Quebec all have separate provincial tax regimes. We handle all of them.
📋 No Surprises — Fixed Price Compliance Plans Before we start any compliance work, you receive a written plan with a fixed price for each jurisdiction. You know exactly what you’re paying before we file anything.
Frequently Asked Questions
Got questions? We’ve got answers.
It depends on where you have nexus — either through physical presence (like FBA warehouses storing your inventory) or economic nexus (exceeding a state's revenue or transaction threshold). Amazon collects Marketplace Facilitator Tax in most states, but you may still have registration and filing obligations. We'll map your exact exposure in a free assessment — and tell you specifically which states you need to register in, which Amazon states require you to file even though Amazon collects, and whether any back liability needs to be addressed before you register.
Since the 2018 South Dakota v. Wayfair Supreme Court decision, most US states can require out-of-state sellers to collect sales tax once they exceed a certain sales volume — typically $100,000 in revenue or 200 transactions per year. If you sell on Amazon or Shopify and ship to customers in multiple states, you almost certainly have economic nexus in several of them.
Yes, if you sell into the US and exceed state economic nexus thresholds, you have the same obligations as a US-based seller. Selling from Canada does not exempt you from US state sales tax laws. We help Canadian sellers navigate both their US obligations and their Canadian GST/HST requirements simultaneously.
GST/HST is Canada's federal goods and services tax. If your worldwide taxable supplies exceed CAD $30,000 in any 12-month period, you're required to register for a GST/HST number and begin collecting and remitting. Most active e-commerce sellers in Canada cross this threshold quickly. We handle the registration, setup, and ongoing filings with the CRA.
GST (5%) is the federal tax collected across Canada. HST is a combined federal + provincial tax used in Ontario, Nova Scotia, New Brunswick, PEI, and Newfoundland. PST is a separate provincial tax in BC, Saskatchewan, and Manitoba. QST is Quebec's provincial sales tax, administered separately from GST. As a seller, your obligations depend on where your customers are located and what you're selling. We map this out for you as part of our nexus analysis.
Not necessarily — but the sooner you act, the better. Voluntary disclosure programs exist in most US states and with the CRA in Canada that allow you to come forward proactively, limit your look-back period, and significantly reduce or eliminate penalties. We handle VDA and CRA VDP applications regularly and can assess your best path forward in a free consultation.
Not entirely. In most US states, Amazon collects and remits sales tax on your behalf as a Marketplace Facilitator — which means you're covered for the sales tax on individual transactions. However, you may still have registration obligations in states where you have nexus, and certain states require sellers to file returns even if the marketplace collects for you. You may also have obligations for sales through your own website, direct channels, or non-marketplace sales. A nexus analysis clarifies exactly what remains your responsibility.
A VDA is a formal agreement between you and a US state that allows you to come forward voluntarily and disclose past unregistered sales tax liability. In exchange, states typically limit the look-back period (usually to 3–4 years instead of unlimited), reduce or waive penalties, and provide a structured payment plan for any back tax owed. VDAs are almost always better than waiting to be discovered. If you have unregistered nexus in multiple states, a coordinated multi-state VDA programme can resolve your entire US exposure at once. We manage this process from start to finish.
A registered but non-filing seller is actually at higher risk than an unregistered one in many states — because the state already knows you exist and can see missing returns in their system. This typically triggers automated penalty notices and may escalate to audit. The right approach is to file back returns as quickly as possible, often alongside a penalty abatement request. We assess the most efficient path to full compliance and handle the filing process for you.
If you are a Canadian-based seller and your worldwide taxable supplies exceed CAD $30,000 in any 12-month period, yes — you must collect and remit GST/HST on sales to Canadian customers, regardless of the platform. If you are a non-resident seller (e.g., US-based selling into Canada), you may also have GST/HST obligations depending on your sales volume and business structure. As of 2021, non-resident digital service providers also face federal registration requirements above certain thresholds. We assess your specific situation and handle everything with the CRA.
Explore common queries about working with Thelonex. Still unsure?
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Non-Compliance Doesn't Stay Hidden — It Gets More Expensive Every Month.
Every month without compliance is another month of penalty exposure. Every state you're unregistered in is a potential audit notice. And every day you delay is a day more transactions are unaccounted for. We assess your full exposure — US and Canada — give you a fixed-price compliance plan, and handle everything from registration to ongoing filing. One team. Both countries. No more guessing.