A1Flow: invoices to accounts

The problem

Every quarter, the firm typed hundreds of its clients' invoices into the accounting software by hand. Four things made it hard to automate.

• Hours of repetitive typing

  Date, number, tax ID, bases, VAT rates, withholdings… one invoice at a time.

• Messy documents

  Scans, phone photos, PDFs with several invoices inside, credit notes, disbursements, reverse charge, foreign tax IDs.

• Strict import formats

  CONTASOL and Contasimple only accept Excel files with exact columns, codes and numbering. One mistake and the import fails or the books don't balance.

• Companies and sole traders differ

  Sole traders keep different books, and you need to know whether an expense is deductible for their line of business.

The process

1. Phase 1

   Understand the firm

   Sitting with the team to follow an invoice from start to finish, and what CONTASOL expects in every column.

2. Phase 2

   Extraction pipeline

   Split, read, extract with an LLM and validate with accounting rules.

3. Phase 3

   Human review

   Those that don't balance wait in 'Review required' and get fixed with the PDF alongside. The rest go straight through.

4. Phase 4

   Accounting exporters

   VAT ledgers, third parties, a double-entry journal and sole-trader records, built from the official templates.

5. Phase 5

   Production

   The firm's Windows server with Caddy and automatic HTTPS, in use from the first month and iterated weekly.

From PDF to spreadsheet row

The model

The rules that make it hard

Reading a simple invoice is easy. These are the ones that aren't, and each changes what gets written in the ledger and the journal.

• Several VAT rates

  A single invoice produces several ledger lines and several journal entries.

• Credit notes and refunds

  Negative amounts, a reference to the original invoice and their own treatment in the journal.

• Withholding, disbursements, reverse charge

  Each one changes which accounts are used and how the total balances.

• Linked numbering

  The entry code in the journal must match the record in the VAT ledger, or CONTASOL won't link them.

• Non-deductible expenses

  Depending on the company's or sole trader's activity, expenses unrelated to the business are flagged.

• Statuses with accents

  'Revisión requerida' versus 'revision': a silent bug that kept a button disabled for months, until diacritics were normalised in every comparison.

The project in numbers

• 8accounting export formats
• 2accounting packages
• 70 %of invoices read without paid OCR
• 70automated tests
• 30.000lines across 87 files and 43 commits
• 4months, in production from the first

What I took away

• Measure before optimising

  Before changing the OCR, a script compared the approaches on real invoices: on digital ones, the PDF's text got 85.9% right against 84.6% for OCR. The cheap option was also the best one.

• The LLM proposes, the rules decide

  The model extracts; validating amounts and tax IDs decides whether the invoice is trustworthy or goes to review.

• The import format is the contract

  Every exporter is tested against the official templates, because an almost-correct spreadsheet is useless.

• Authorisation always on the server

  Plus short-lived signed URLs for viewing the invoice PDFs.

And in your case?