Technical Deep Dive

How AI Document Processing Works in 2025

Understanding the technology stack behind 99.9% accurate invoice data extraction: OCR, NLP, computer vision, and machine learning models explained.

12 min read Quixyl Engineering Team
AI Document Processing Architecture

The AI Document Processing Pipeline

Modern AI document processing combines multiple technologies to achieve human-level accuracy in data extraction. Let's break down each stage of the pipeline that processes your invoices in under 5 seconds.

The 5-Stage AI Processing Pipeline

  1. 1
    Document Upload & Preprocessing

    Image optimization, format conversion, and quality enhancement

  2. 2
    Optical Character Recognition (OCR)

    Text extraction using Azure Document Intelligence and custom models

  3. 3
    Layout Analysis & Document Understanding

    Computer vision identifies tables, fields, and document structure

  4. 4
    Named Entity Recognition (NER)

    ML models identify vendor names, amounts, dates, invoice numbers

  5. 5
    Validation & Confidence Scoring

    Cross-referencing, format validation, and accuracy confidence metrics

Stage 1: Document Preprocessing

Before any AI processing begins, documents undergo critical preprocessing to ensure optimal extraction quality:

Image Quality Enhancement

  • Deskewing: Automatically corrects document rotation up to 30 degrees using computer vision
  • Denoising: Removes background artifacts, watermarks, and compression noise
  • Binarization: Converts images to optimal contrast for text recognition
  • DPI Normalization: Upscales low-resolution images to 300 DPI for better OCR accuracy

Stage 2: Optical Character Recognition (OCR)

OCR is the foundation of document processing. Quixyl uses Azure Document Intelligence combined with custom-trained models to achieve industry-leading accuracy.

How Modern OCR Works

1. Character Detection
   └─ Deep CNN identifies character bounding boxes
   └─ Processes 300+ characters per second

2. Character Recognition
   └─ Transformer model predicts characters from images
   └─ Supports 123 languages + handwriting
   └─ 99.7% accuracy on printed text

3. Context Understanding
   └─ Language model corrects OCR errors using context
   └─ Handles common OCR mistakes (O/0, I/l/1)
   └─ Improves accuracy to 99.9%

Key OCR Technologies

Tesseract OCR (Open Source)

  • • 100+ language support
  • • 95-98% accuracy on clean documents
  • • Struggles with tables and layouts
  • • Used as fallback for uncommon languages

Azure Document Intelligence

  • • 99.7% accuracy out-of-box
  • • Understands document layout
  • • Pre-trained on millions of invoices
  • • Handles tables, forms, and checkboxes

Stage 3: Layout Analysis & Document Understanding

Raw text isn't enough. AI needs to understand the structure of your document to extract meaningful data.

Computer Vision for Layout Detection

Our computer vision models are trained on 50,000+ invoice layouts to identify:

  • Tables: Line items, tax breakdowns, quantity × price calculations
  • Key-Value Pairs: "Invoice Number: INV-001" or "Total: $1,250.00"
  • Sections: Header, body, footer, payment terms, line items
  • Logos & Branding: Vendor identification through visual features

Stage 4: Named Entity Recognition (NER)

NER is where AI gets "smart". Machine learning models identify and classify specific data points from unstructured text.

What NER Extracts

Financial Entities

  • • Invoice total amount
  • • Tax amounts (VAT, GST, Sales Tax)
  • • Subtotals and discounts
  • • Currency codes (USD, EUR, GBP)
  • • Payment terms (Net 30, Due on Receipt)

Metadata Entities

  • • Invoice numbers (various formats)
  • • Purchase order (PO) numbers
  • • Dates (invoice, due, service dates)
  • • Vendor names and addresses
  • • Customer/Bill-to information

How NER Models Are Trained

Quixyl's NER models are fine-tuned on millions of real-world invoices:

  1. 1. Base Model: Start with pre-trained BERT or DistilBERT transformer
  2. 2. Invoice-Specific Training: Fine-tune on 2M+ labeled invoice fields
  3. 3. Active Learning: Continuously improve using customer corrections and feedback
  4. 4. Multi-Language Support: Separate models for different languages and regions

Stage 5: Validation & Confidence Scoring

The final stage ensures data quality through multiple validation checks and confidence scoring.

Validation Rules Engine

  • Math Validation: Verify subtotal + tax = total, check line item calculations
  • Format Validation: Ensure dates are valid, amounts have proper decimals
  • Business Logic: Flag invoices with suspicious amounts or duplicate numbers
  • Cross-Field Validation: Check consistency across related fields

Confidence Scoring

Every extracted field receives a confidence score (0-100%) based on:

  • • OCR quality and character clarity
  • • NER model certainty
  • • Validation rule passes
  • • Historical extraction patterns

Confidence Thresholds

95-100%: High confidence, auto-approved
80-94%: Medium confidence, flagged for review
Below 80%: Low confidence, requires manual verification

Advanced AI Features

Custom Template Learning

Quixyl learns your specific invoice formats over time. After processing 5-10 invoices from the same vendor, accuracy improves to 99.95% as the system creates a custom template for that vendor's layout.

Handwriting Recognition

Advanced neural networks trained on millions of handwriting samples can extract handwritten notes, signatures, and filled forms with 92-95% accuracy.

Multi-Page Document Intelligence

AI automatically identifies page relationships, combines data from multi-page invoices, and handles attachments like purchase orders or delivery notes.

Performance Metrics

99.9%
Field Accuracy
<5s
Processing Time
123
Languages Supported

Conclusion

Modern AI document processing combines OCR, computer vision, NLP, and machine learning into a sophisticated pipeline that rivals human accuracy while processing documents in seconds instead of minutes.

Quixyl leverages Azure Document Intelligence, custom-trained NER models, and advanced validation logic to deliver 99.9% accurate invoice data extraction at scale.

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