Billy API review
A low-cost REST API for invoices, ledger data and accounting workflows in Billy.
Reviewed by iTechGuides Editors · Editorial team · Updated Oct 2026
Billy API connects external software with Billy, an online accounting platform for Danish small businesses and self-employed users. Its JSON-based REST API covers invoices, contacts, products, product prices, daybook transactions, transaction lines, postings, payments, accounts and tax data. Developers can read, create, update and delete many resources, while paging, filtering, sorting and multiple localization options support data workflows. Authentication is available through access tokens or HTTP Basic Auth, and the service is offered across web and API environments.
Pricing follows Billy’s accounting plans. Free costs 0 DKK per month and includes the accounting system, invoicing, VAT reporting, email and chat support, and receipt upload. Basic costs 160 DKK per month and adds no usage limits, ad-free invoices, accounting support, and accountant access. Plus costs 295 DKK per month and adds advanced AI accounting features, Copilot access, unlimited integrations, and phone support. Complete costs 595 DKK per month and adds quarterly accounting review and priority accounting support. A 30-day free trial is also available, with monthly prices displayed in DKK excluding VAT.
The main fit is for teams that already work in Billy and need direct access to invoice and ledger resources through a conventional REST interface. The API’s coverage suits synchronization, transaction access, payment associations and localized accounting workflows. Its narrower Billy-centered scope makes it less suitable for organizations seeking a neutral accounting API across multiple platforms. Buyers should also distinguish the accounting subscription tiers from the API’s technical surface: higher plans add operational accounting benefits such as unlimited integrations, Copilot and priority support, while the core API value is its access to Billy data and workflows.
Billy API pros and cons
- Where it wins
- Free plan with invoice, ledger, payment and contact access
- Supports invoice CRUD, filtering, sorting and pagination
- Access tokens and HTTP Basic Auth support integration flexibility
- Where it doesn't
- Focused on Billy rather than a broad accounting ecosystem
- Unlimited integrations begin with the Plus plan
- Phone and priority accounting support are limited to higher tiers
Billy API fact sheet, pricing and score →
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