If your software company sells into more than one US state or more than one country, there's a legal tripwire most founders don't hear about until it's already a problem: once your revenue in a given place crosses a threshold, you're suddenly required to register for and collect sales tax or VAT there. Nobody sends you a calendar invite for this — you usually find out when a notice from a state tax authority shows up in the mail, or an accountant flags it during a fundraise. The tools below exist to solve that in two different ways: three full-service platforms that watch your thresholds and handle registration, filing and remittance for you, and two lightweight APIs that just validate a customer's VAT number at checkout.
The short version
If you're a growing SaaS company and haven't touched sales tax compliance yet, start with Numeral — its free tier just watches your nexus thresholds and costs nothing until you actually need to file. If you're already past that stage and want the deepest billing-platform integration, Anrok is built specifically for SaaS billing data. If you're already late on a filing deadline and need to be compliant fast, Sphere claims sub-24-hour setup with 24/7 human backup on Slack. If all you need is to validate a customer's VAT number at checkout — not full compliance — vatlayer or vatcheckapi.com are far cheaper, simpler tools for that one job.
Anrok
For: SaaS and software companies with US multi-state or international sales, whose finance team needs nexus monitoring built around modern billing data rather than retail transactions.
Price: Paid only, no free tier. Starter is $50/market/month for eCommerce or $100/market/month for other companies, where a "market" is one US state or one country you're registered in. High-volume sellers get a custom, transaction-based plan.
Anrok's pitch is that it was built by and for SaaS companies, and that shows in how cleanly it plugs into Stripe, NetSuite, Salesforce, Shopify and 40+ other billing/ERP systems, plus a headless tax-calculation API if you need custom checkout logic. It monitors nexus across 150+ countries and 11,000+ US jurisdictions in real time, then handles registration, calculation, filing and remittance, and manages exemption certificates too.
Honest limits: there's no free tier at all — costs start the moment you add a market, and they scale linearly, so a wide multi-state or multi-country footprint gets expensive fast. It's also a younger vendor than legacy players like Avalara for pure retail or marketplace tax.
Numeral
For: companies that aren't sure yet whether they've crossed a nexus threshold anywhere, and want to find out before committing to a paid tool.
Price: Freemium. The free tier covers nexus study, monitoring and alerts only — no cost to just watch your thresholds. The paid Professional tier adds full filing and remittance, with per-filing/registration fees disclosed during onboarding rather than published upfront.
Numeral automates sales tax, VAT and GST compliance across 70+ countries: nexus monitoring, automated registration, filing, remittance, and exemption certificate collection. Its more unusual feature is a virtual mailbox with AI scanning — physical tax notices get flagged automatically instead of sitting in a drawer — plus AI monitoring of government tax portals directly for changes. It's raised $57M from Benchmark, Mayfield and Y Combinator.
Honest limits: the full paid-tier pricing isn't published anywhere, so you need to go through onboarding to get real numbers. Once you're past the free tier, its feature set converges heavily with Anrok and Sphere — the free monitoring option is really its main differentiator.
Sphere
For: fast-growing companies with international sales that need to get compliant quickly, especially if they're already past a filing deadline.
Price: Paid only. Starter is $100/region/month for under 10 regions; Growth tier is custom pricing for 10+ regions with a dedicated account manager, plus per-transaction fees above 50,000 monthly transactions.
Sphere's specific pitch against Anrok and Numeral isn't different core functionality — all three cover nexus monitoring, calculation, filing and remittance across 100+ jurisdictions — it's speed of setup and always-on human backup. It claims sub-24-hour implementation versus the multi-week onboarding typical elsewhere, built on an AI model it calls TRAM (Tax Review and Assessment Model) trained on tax law, plus a human tax team reachable on Slack 24/7. It's raised a $21M Series A.
Honest limits: no free tier, and its $100/region/month starter rate matches Anrok's higher tier while being pricier than Anrok's eCommerce rate. Its breadth claim of 100+ jurisdictions from a young company raises fair questions about how deep its expertise goes in any single one of them.
vatlayer
For: developers who just need to validate EU VAT numbers and pull VAT rates programmatically — not full compliance automation.
Price: Freemium. 100 free API requests per month; paid tiers exist but pricing isn't clearly published.
vatlayer is a narrow, simple API: instant VAT number validation plus access to EU VAT rates. If your only tax-compliance need is checking that a B2B customer's VAT number is real before you zero-rate an invoice, this does that one job without pulling in a whole platform.
Honest limits: support response times have been reported as slow, and paid pricing above the free tier isn't transparent on the site.
vatcheckapi.com
For: small businesses or freelancers who need occasional VAT number validation and want to stay on a free plan.
Price: Free, 150 validations per month.
Same core job as vatlayer — VAT number lookup and validation — but with a more generous free allowance (150 vs. vatlayer's 100 requests/month) and no paid tier to think about at small volume.
Honest limits: it's a much less established name than competitors, lacks advanced features like detailed reporting, and what happens if you exceed the free 150 validations isn't clearly documented.
| Tool | Scope | Pricing | Free tier? | Best for |
|---|---|---|---|---|
| Anrok | Full compliance (150+ countries, 11,000+ US jurisdictions) | $50–100/market/month | No | SaaS billing-native integration |
| Numeral | Full compliance (70+ countries) | Custom (paid tier) | Yes — monitoring only | Testing the waters before paying |
| Sphere | Full compliance (100+ jurisdictions) | $100/region/month | No | Fast setup, 24/7 human support |
| vatlayer | VAT number validation + EU rates | Free / unclear paid | Yes — 100 req/month | Lightweight VAT lookup for developers |
| vatcheckapi.com | VAT number validation | Free | Yes — 150 req/month | Occasional validation, freelancers |
None of these tools replace an actual tax accountant for edge cases, but for the day-to-day grind of monitoring thresholds and filing on time, Numeral's free tier is the lowest-risk starting point, Anrok and Sphere are the two real contenders once you're paying for full automation, and vatlayer or vatcheckapi.com cover the much narrower job of checking a VAT number is real. Pick based on how far along you actually are — not sure you've crossed a threshold anywhere, or already know you need full filing across a dozen jurisdictions.