Once a software or e-commerce business starts selling into enough countries or US states, it crosses invisible thresholds — called nexus — where it suddenly owes sales tax, VAT or GST somewhere it didn't before. Figuring out where those thresholds are, calculating the right rate, and actually filing the paperwork is tedious enough that an entire category of tools exists just to automate it. Quaderno and Kintsugi both promise to handle this, but they're built around two different bets on how you'll want to pay for it.
Quaderno: pay a flat fee, get everything from day one
Quaderno calculates tax in real time across more than 12,000 tax jurisdictions worldwide and generates localized invoices automatically — in the customer's own language and currency. It's been through a 2023 acquisition by the Visma group but still operates as its own product. The core appeal is transparency: published plans starting at $29/month (Hobby, 25 transactions) up to $149/month (Growth, 2,500 transactions), so you know the cost before you talk to anyone.
The honest limit: Quaderno is stronger at calculating and invoicing than at the harder back-office work of registering your business and filing returns in each jurisdiction — for that, you're often still doing manual work or pairing it with an accountant. And because pricing scales with transaction volume, a fast-growing business can outgrow the flat tiers faster than expected.
Kintsugi: free to watch, pay only once you owe
Kintsugi flips the pricing model: nexus monitoring — the part that tells you where you're approaching a tax obligation — is free. You only start paying once you actually need to register and file, at $75 per return, or a $500/month Premium plan once you're filing across up to 7 states. It covers US sales tax plus VAT/GST in 106 countries, with native integrations into Stripe, Chargebee, Shopify, QuickBooks and NetSuite, and picked up a 2025 investment/partnership with Vertex, an established name in tax technology.
The tradeoff is that Kintsugi is a narrow, specialized tool — genuinely useful once you have real multi-state or international exposure, but overkill before that point. And the per-filing pricing, while cheap at low volume, can end up costing more than a flat-fee competitor once you're registered in many states at once.
Side by side
| Quaderno | Kintsugi | |
|---|---|---|
| Pricing model | Flat monthly tiers ($29-$149+) | Free monitoring, pay per filing ($75) or $500/mo Premium |
| Coverage | 12,000+ jurisdictions worldwide | US states + 106 countries for VAT/GST |
| Strongest at | Real-time calculation + localized invoicing | Nexus monitoring + registration/filing |
| Integrations | General invoicing/billing focus | Stripe, Chargebee, Shopify, QuickBooks, NetSuite |
| Free trial | 7 days | Nexus monitoring free indefinitely |
| Backing | Visma group (2023 acquisition) | Vertex Inc. investment/partnership (2025) |
Pick Quaderno if… / Pick Kintsugi if…
Pick Quaderno if you're already selling internationally and want one predictable monthly bill that covers calculation and invoicing across essentially every jurisdiction that exists, without a sales call. Pick Kintsugi if you're not sure yet where you owe tax — its free nexus monitoring lets you watch your exposure grow without paying anything, and you only start paying once registration is actually necessary.
The honest bottom line: this is really a question of what stage you're at. A pre-threshold startup has no reason to pay Quaderno's flat fee before it owes tax anywhere — Kintsugi's free monitoring is the better fit. A business already filing in a dozen countries is often better off with Quaderno's flat pricing than paying per return everywhere it operates.