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CRM/ERP

Invoicing API for Custom CRM/ERP

Plug-and-play invoicing module for your internal system

Add professional invoicing capabilities to your CRM or ERP without building the entire tax system from scratch. Integrate in days, not months. Spanish regulatory compliance without writing a single line of tax logic.

Why not build your own invoicing engine?

Building in-house invoicing seems simple until you face the complexity of Spanish tax law.

Underestimated tax complexity

Invoicing in Spain means handling VAT (4%, 10%, 21%, exempt, intra-community), income tax withholding (professionals, rentals), VeriFactu with digital fingerprint, mandatory sequential numbering, credit notes, and annual regulatory changes. That's months of development and ongoing maintenance.

VeriFactu and fiscal blockchain

Since 2025, invoices must include a digital fingerprint calculated with the official AEAT algorithm and be chained to the previous one. Implementing this correctly requires deep knowledge of cryptography and VeriFactu regulations. One mistake and your invoices are invalid.

Perpetual regulatory maintenance

Tax regulations change constantly: VAT rates, mandatory formats, new required fields. If you build your own system, your team must keep up with every change and update the code. It's a hidden cost that never ends.

Professional PDF generation

Storing data in a database isn't enough. You need to generate A4 PDFs, multi-language (ES, EN, CA), with your logo, proper layout, and readable tax breakdowns. PDF libraries + design + translations is non-trivial work.

Integration with external systems

Your CRM/ERP probably needs to integrate with accounting (Sage, A3, Holded), commercial CRMs (Salesforce, HubSpot), or export to Excel/CSV for accountants. Building all these exports takes time and adds no competitive advantage.

Development time vs. time-to-market

Building a complete invoicing engine can take 3-6 months of development. With the BeeL. API, you integrate in days. That saved time can be invested in features that truly differentiate your product.

How to integrate invoicing into your custom CRM/ERP

A simple API-first integration process that adapts to any software architecture.

1

Store BeeL. client_id in your database

When you create a client in your CRM, you POST /clients to BeeL. You receive a client_id that you store in your clients table alongside your internal data.

  • Your clients table adds a beel_client_id column
  • You sync name, tax ID, address, email with BeeL.
  • You can update data with PUT /clients/:id if they change
2

Map products/services to BeeL.

If you have a product catalog, create them in BeeL. with POST /products. Store product_id to reuse them in future invoices. If you don't use a catalog, send line items directly when invoicing.

  • Each product has a description, base price, VAT type
  • Optional: you can invoice without a catalog by sending ad-hoc line items
  • Useful if you sell customized services for each sale
3

Issue invoices from your sales workflow

When you close a deal/opportunity in your CRM, your code calls POST /invoices. You send client_id, sale line items, and an idempotency key (e.g., opportunity_id).

  • BeeL. validates data, calculates VAT, generates sequential numbering
  • You receive an invoice_id to store in your CRM
  • If you need a draft invoice, you can create it without issuing
4

PDF generated and sent automatically

BeeL. generates the PDF with your branding and sends it by email to the client. You can download it via API if you need to display it in your CRM interface.

  • GET /invoices/:id/pdf downloads the PDF
  • POST /invoices/:id/send resends the email if needed
  • PDF includes VeriFactu, QR, and AEAT compliance
5

Query and reporting from your CRM

With GET /invoices you can list all your invoices filtered by date, client, status. Use this data for dashboards, financial reports or accounting exports.

  • Filters: start_date, end_date, client_id, status
  • Pagination for large volumes
  • Export JSON for accounting ERP integrations

Advantages of outsourcing invoicing vs. building it

Reduced development costs, zero maintenance, and guaranteed compliance.

Integration in days, not months

Connecting your CRM to BeeL.'s API takes days of development. Building a complete invoicing system can take 3-6 months. You ship business features faster.

Effortless regulatory compliance

VeriFactu, AEAT, VAT, income tax... all the complexity managed by BeeL. Your team doesn't need to be Spanish tax experts — they can focus on your business domain.

Zero regulatory maintenance

When tax law changes (and it changes every year), BeeL. updates the API automatically. Your code keeps working without modifications. No hidden maintenance cost.

Technical scalability included

The API supports 1000 req/hour by default. If you grow beyond that, enterprise plans with higher rate limits. No need to scale your own invoicing infrastructure.

FAQ about CRM/ERP integration

Can I migrate historical invoices to BeeL.?

No. BeeL. generates invoices with sequential numbering from the moment you activate your account. You cannot import old invoices because it would break the sequence and VeriFactu. What you can do is start using BeeL. now and keep old invoices in your current system for reference.

Does the API support multi-tenant (multiple clients from my CRM)?

If your CRM is SaaS and has multiple companies as clients, each company needs its own BeeL. account and API key. You cannot invoice on behalf of your clients with your API key. Each fiscal entity is independent.

Can I fully customize invoice fields?

You can customize descriptions, add footnotes, and configure your branding (logo, colors). However, mandatory tax fields (tax ID, taxable base, VAT, etc.) cannot be modified because they are regulated by the AEAT. This ensures legal compliance.

How do I manage invoice series (F-, FR-, FC-)?

BeeL. manages numbering series automatically. You can have separate series for standard invoices (F-), credit notes (FR-), simplified invoices (FS-). When creating the invoice, you specify the type and BeeL. assigns the correct number from the corresponding series.

Can I use BeeL. just to generate PDFs without fiscal issuance?

No. BeeL. is a complete fiscal invoicing system, not a PDF generator. Every issued invoice has legal and tax effects (VAT, income tax, VeriFactu). If you only need PDFs without fiscal validity, use document generation libraries (Puppeteer, PDFKit, etc.).

Ready to automate your invoicing?

Integrate BeeL.'s API and start invoicing in minutes.