INVOICING SOFTWARE WITH VERIFACTU AND AI
Bilteo

Bilteo is an invoicing SaaS for freelancers, small businesses and accountants, built from scratch around VeriFactu, the Spanish Tax Agency system that requires every issued invoice to produce a chained, tamper-proof record and be reported immediately.

It is not a bolt-on to an existing app: compliance is the core of the product. Every sale generates its record, sealed with a SHA-256 hash linked to the previous one to form an unbreakable chain, sent to the tax agency, with the verdict handled automatically —corrections and re-submissions included. The PDF ships with its official verification QR code.

On that legal foundation, Bilteo puts artificial intelligence exactly where self-employed people lose time: you say what you are charging and the AI writes the line item, works out VAT and withholdings and leaves the invoice ready to issue. For expenses a photo of the receipt is enough: the OCR scanner pulls out merchant, date, net amount, VAT and total and drafts the purchase invoice.

Architecture: multi-tenant Go backend (Gin + GORM), a Vue 3 + Quasar app installable as a PWA, a Python / FastAPI microservice for PDFs, a Django marketing site and public developer docs, all on PostgreSQL and Redis with async queues, Stripe subscriptions, AWS KMS certificate encryption, Docker and GitLab CI/CD.

From 1 January 2027 for corporate taxpayers, and 1 July 2027 for every other business and freelancer in Spain, invoicing must be done with a system that complies with RD 1007/2023. Thousands of businesses still invoicing with Excel, Word or legacy programs will have to switch, and the software vendor is legally answerable for the integrity and traceability of the records.

The goal was to build exactly that software: an invoicing system that meets the regulation down to the detail and still feels easy to someone who knows nothing about tax. A modern alternative to tools like Holded, Quipu or Factorial, designed for the self-employed first.

Hence the three lines of work:

• Compliance with no margin for error: hash chaining, immutability once a record is generated, asynchronous submission with retries, handling of corrections and rejections, and full traceability. Nothing is deleted: mistakes are fixed with corrective invoices and cancellations, as the law requires.
• AI to remove friction: creating an invoice should be describing what you charge, and logging an expense should be taking a photo.
• Openness: any third-party software should be able to lean on Bilteo to comply with VeriFactu without rewriting its own invoicing, through the public API and Bilteo Direct.

All of it on a multi-tenant architecture with strict per-customer data isolation, a real sandbox against the tax agency test environment and continuous deployment.

Bilteo is in production as VeriFactu invoicing software, with the app, the public API, the developer documentation and the multilingual site all running on the same platform.

• Automatic chained filing with the tax agency for every issued invoice, with SHA-256 hash, verification QR on the PDF and full handling of the official verdicts.
• Complete invoicing cycle: full, simplified and substitute invoices, corrective invoices R1–R5, cancellations and automatic recurring invoices.
• Built-in AI: invoices created from a plain description, and an OCR scanner for receipts and supplier invoices that drafts the expense for you.
• Two integration routes for third parties: a versioned REST public API with OpenAPI 3.1, scoped API keys and webhooks; and Bilteo Direct, a single endpoint to file invoices already issued by another system.
• Isolated sandbox against the tax agency test environment, with test watermarks on documents and data kept apart from production.
• Multi-tenant and multilingual (Spanish, Catalan and English) across app, documentation and content.
• Security: certificate private keys protected with envelope encryption on AWS KMS, granular role-based permissions and two-factor authentication.
• AI-assisted development end to end, with agents working from a technical guide to the repository and automated quality gates in CI.