Automate Invoice Processing

A review-centered invoice workflow

Invoice data is often copied into accounting systems or spreadsheets. PDF extraction can prepare content for review, but it should not be treated as an automatic approval or a substitute for checking the source.

Building an Invoice Automation Pipeline

Architecture Overview

Select PDF → Extract available content → Review against source → Use in your own workflow

Step 1: Invoice Ingestion

import imaplib
import email
from pathlib import Path

def fetch_invoice_emails(imap_server, credentials):
    """Fetch PDF attachments from invoice emails"""
    conn = imaplib.IMAP4_SSL(imap_server)
    conn.login(credentials['user'], credentials['password'])
    conn.select('INBOX')
    
    # Search for emails with PDF attachments
    _, messages = conn.search(None, 'UNSEEN')
    
    invoices = []
    for msg_id in messages[0].split():
        _, msg_data = conn.fetch(msg_id, '(RFC822)')
        email_body = email.message_from_bytes(msg_data[0][1])
        
        for part in email_body.walk():
            if part.get_filename() and part.get_filename().endswith('.pdf'):
                pdf_data = part.get_payload(decode=True)
                invoices.append({
                    'filename': part.get_filename(),
                    'data': pdf_data,
                    'sender': email_body['From'],
                    'received': email_body['Date']
                })
    
    return invoices

Step 2: Extract and review

PDFDrill supports table extraction to Excel or CSV, OCR text extraction from scanned PDFs, AI-assisted cleanup, and AI-assisted JSON output without custom schemas. Review exported content against the source PDF before reusing it.

The following fictional values illustrate the kinds of details a person may review; this is not a promised PDFDrill output:

{
  "vendor": {
    "name": "ABC Supplies Inc",
    "address": "123 Business Ave, City, ST 12345",
    "tax_id": "12-3456789",
    "bank_account": "****1234"
  },
  "invoice": {
    "number": "INV-2024-5678",
    "date": "2024-11-27",
    "due_date": "2024-12-27",
    "po_number": "PO-9876"
  },
  "line_items": [
    {
      "description": "Office Supplies - Paper",
      "sku": "SUP-001",
      "quantity": 50,
      "unit_price": 12.00,
      "total": 600.00
    },
    {
      "description": "Office Supplies - Pens",
      "sku": "SUP-002", 
      "quantity": 100,
      "unit_price": 2.50,
      "total": 250.00
    }
  ],
  "totals": {
    "subtotal": 850.00,
    "tax_rate": 0.08,
    "tax_amount": 68.00,
    "total": 918.00
  }
}

Step 3: Check reviewed values

def subtotal_matches(items, subtotal):
    calculated = sum(item["total"] for item in items)
    return round(calculated, 2) == round(subtotal, 2)

This arithmetic check only examines values supplied to it. It does not confirm that extracted data is complete or correct.

Best Practices

1. Compare key fields, line items, and totals with the source PDF.
2. Correct discrepancies in your own review process.
3. Enter approved information into your accounting workflow.

PDFDrill does not automatically approve invoices or guarantee direct integrations with accounting systems. The Business API uses Bearer authorization; consult the current API documentation for supported usage.

Conclusion

Invoice processing can use PDF extraction to reduce repetitive copying, while review remains important for financial records. PDFDrill provides table extraction, OCR text extraction, AI-assisted cleanup, and AI-assisted JSON output. Try PDFDrill free: 10 pages a month.