👉 Try the demo: https://github.com/LM-Kit/lm-kit-net-samples/tree/main/console_net/receipt_expense_scanner

AI Receipt & Expense Scanner for C# .NET Applications

🎯 Purpose of the Demo

AI Receipt & Expense Scanner demonstrates how to use LM-Kit.NET to extract structured expense data from receipts entirely on local hardware. Feed it any receipt and get back structured JSON with store info, line items, totals, tax breakdown, payment details, and an automatic expense category.

The sample shows how to:

Use TextExtraction to extract structured data from receipt text.
Define extraction schemas with TextExtractionElement including line item arrays.
Automatically categorize expenses (Meals, Office Supplies, Travel, Groceries, etc.).
Parse text content with SetContent(string) or load documents/images with Attachment.

Why a Local Receipt Scanner with LM-Kit.NET?

Financial data stays private: process expense receipts without uploading to cloud services.
One API call: a single Parse() call extracts all receipt data. No agents, no chaining.
Line item detail: each purchased item extracted with quantity, unit price, and total.
Works offline: no API keys, no internet connection required.

👥 Who Should Use This Demo

Finance Teams: automate receipt processing for expense reports.
Accountants: extract structured data from receipts for bookkeeping.
Small Business Owners: digitize paper receipts for tax preparation.
Expense Management Developers: integrate local receipt scanning into expense apps.
Developers: learn the TextExtraction API with nested array elements for line items.

🚀 What Problem It Solves

Manual data entry: eliminate typing receipt details into expense reports.
Data privacy: process receipts with sensitive financial data without cloud exposure.
Categorization: automatically classify expenses into accounting categories.
Integration: produce JSON output ready for accounting software or ERP systems.

💻 Demo Application Overview

Console app that:

Lets you choose from multiple models optimized for text extraction.
Downloads models if needed, with live progress updates.
Creates a TextExtraction instance with a receipt-specific schema.
Enters an interactive loop where you can:
- Type sample to scan a built-in grocery store receipt.
- Enter a file path to scan your own receipt (.txt, .pdf, .png, .jpg).
- View the extracted expense data with color-coded output.
- View the full JSON output for integration.
Loops until you type q.

Key Features

Line Item Extraction: Each item parsed with description, quantity, unit price, and total.
Tax Breakdown: Tax rate and tax amount extracted separately.
Auto-Categorization: AI suggests the expense category for accounting.
Built-In Sample: Realistic grocery receipt for instant demo.
JSON Output: Machine-readable structured data for any accounting system.
Zero Configuration: No API keys, no cloud accounts, no external dependencies.

🏗️ Architecture

  ┌─────────────────────────────────────────────────┐
  │           Receipt (text, PDF, image)             │
  └───────────────────┬─────────────────────────────┘
                      │
                      ▼
  ┌─────────────────────────────────────────────────┐
  │              TextExtraction                      │
  │                                                  │
  │   Schema:                                        │
  │   ├── Store Name (String)                        │
  │   ├── Store Address (String)                     │
  │   ├── Date (Date)                                │
  │   ├── Time (String)                              │
  │   ├── Items (Array)                              │
  │   │   ├── Description, Quantity                  │
  │   │   └── Unit Price, Total                      │
  │   ├── Subtotal (Float)                           │
  │   ├── Tax Rate / Tax Amount (Float)              │
  │   ├── Discount (Float)                           │
  │   ├── Total (Float)                              │
  │   ├── Payment Method (String)                    │
  │   ├── Transaction ID (String)                    │
  │   └── Expense Category (String)                  │
  │                                                  │
  └───────────────────┬─────────────────────────────┘
                      │
                      ▼
  ┌─────────────────────────────────────────────────┐
  │           Structured Expense Report              │
  │           (formatted display + JSON)             │
  └─────────────────────────────────────────────────┘

Extraction Schema

Field	Type	Description
Store Name	String	Name of the store or business
Store Address	String	Full address of the store
Date	Date	Transaction date
Time	String	Transaction time
Items	Array	Description, quantity, unit price, line total
Subtotal	Float	Total before tax and discounts
Tax Rate	String	Applied tax rate
Tax Amount	Float	Total tax charged
Discount	Float	Discount applied
Total	Float	Final amount paid
Payment Method	String	Cash, card, etc.
Transaction ID	String	Receipt reference number
Expense Category	String	AI-suggested category

Code Highlights

using LMKit.Extraction;
using LMKit.Model;

LM model = LM.LoadFromModelID("qwen3:8b");

var textExtraction = new TextExtraction(model);
textExtraction.Elements = new List<TextExtractionElement>
{
    new("Store Name", ElementType.String, "Name of the store."),
    new("Date", ElementType.Date, "Transaction date."),
    new("Items",
        new List<TextExtractionElement>
        {
            new("Description", ElementType.String, "Item name."),
            new("Quantity", ElementType.Integer, "Quantity purchased."),
            new("Unit Price", ElementType.Float, "Price per unit."),
            new("Total", ElementType.Float, "Line total.")
        },
        isArray: true,
        "Purchased items."
    ),
    new("Total", ElementType.Float, "Final amount paid."),
    new("Expense Category", ElementType.String, "Suggested category."),
    // ... more elements
};

textExtraction.SetContent(receiptText);
var result = textExtraction.Parse();

Console.WriteLine(result.Json);

⚙️ Getting Started

Prerequisites

.NET 8.0 or later
Sufficient VRAM for the selected model (6-18 GB depending on model choice)

Download

git clone https://github.com/LM-Kit/lm-kit-net-samples
cd lm-kit-net-samples/console_net/receipt_expense_scanner

Run

dotnet build
dotnet run

Then:

Select a model from the menu, or paste a custom model URI.
Wait for the model to download (first run) and load.
Type sample to try the built-in receipt, or enter a file path.
View the extracted expense data and JSON output.
Type q to exit.

🔧 Troubleshooting

Incomplete line items
- Try a larger model (12B+) for better accuracy on receipts with many items.
- Ensure the receipt text is complete and legible.
Image-based receipts
- For receipt photos or scans, use vision-capable models or OCR preprocessing.
- See the invoice_data_extraction demo for image-based extraction.
Incorrect totals
- The model extracts values as-is from the receipt, it does not recalculate.
- Verify the original receipt data is correct.

🚀 Extend the Demo

Batch scanning: process a folder of receipts and generate an expense summary.
Budget tracking: aggregate extracted totals by category over time.
Accounting integration: export JSON to QuickBooks, Xero, or FreshBooks.
Multi-currency: extract and convert currency for international receipts.
Receipt images: combine with vision models for scanning physical receipts.

📚 Additional Resources

How-To: Extract Structured Data: General guide to defining extraction schemas with nested arrays for line items.
How-To: Extract Invoice Data from Documents: Similar extraction workflow applied to invoices with OCR support.
Glossary: Structured Data Extraction: Explains schema-driven extraction concepts used for receipt parsing.
Invoice Data Extraction Demo: Companion demo for extracting structured data from invoice documents.

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