I Built Invoice Parsing That's 15x Faster (Here's How)

The Problem

Every B2B SaaS that deals with finances hits the same wall: How do you extract data from messy invoice PDFs?

I spent 6 months manually parsing invoices for a finance automation tool. It was hell:

• 15 minutes per invoice
• Constant errors (wrong amounts, missed line items)
• Doesn't scale

What I Tried

Attempt 1: Tesseract OCR

import pytesseract
text = pytesseract.image_to_string('invoice.pdf')
# Parse with regex...

60% accuracy, 3 seconds ❌ Too slow, too inaccurate

Attempt 2: Cloud Vision API

const result = await vision.documentTextDetection(invoice);

Better accuracy, still 2 seconds ❌ Still too slow for real-time UX

Attempt 3: GPT-4 Vision

const result = await openai.chat.completions.create({
  model: "gpt-4-vision-preview",
  messages: [{role: "user", content: [...]}]
});

❌ Accurate but $0.50/page, 5 seconds

The Solution

Built Invoice2JSON - custom ML model optimized for invoices.

Architecture

1. Pre-processing Pipeline

   • Deskew rotated scans
   • Enhance low-quality images
   • Detect page orientation

2. Vision Transformer

   • Understands document layout
   • Identifies regions (header, line items, total)
   • Context-aware extraction

3. Field Extraction

   • NER model for specific fields
   • Confidence scoring per field
   • Multi-page aggregation

4. Post-processing

   • Data validation
   • Currency normalization
   • JSON structure

Performance Optimizations

1. Rust Backend
   Python: 847ms average
   Rust: 142ms average (6x faster)

2. Edge Processing
   Cloudflare Workers in 200+ cities
   Reduced latency by 40%

3. Model Quantization
   FP32 model: 234ms
   INT8 model: 142ms (same accuracy!)

4. Async Architecture
   Webhook-first design
   No blocking requests
   Scales to 10K req/sec

Results

Before vs After comparison:

Try It

const Invoice2JSON = require('invoice2json');
const client = new Invoice2JSON('sk_...');

const invoice = await client.parse('./invoice.pdf');
console.log(invoice.data);

// Output (142ms later):
// {
//   vendor: "Acme Corp",
//   total: 1250.00,
//   date: "2024-01-15",
//   line_items: [...],
//   confidence: 0.998
// }

Free tier: invoice2json.com (25 invoices/month)

Questions?

Drop them in the comments! Happy to share more technical details.