# Examples & Patterns

These are production apps built on Bkper, each demonstrating a different integration pattern. All are open source and available on GitHub.

## Tax Bot

[GitHub](https://github.com/bkper/bkper-tax-bot)

Calculates VAT, GST, and other taxes automatically when transactions are posted. Demonstrates **property-driven configuration** — tax rates and rules are stored in account and group properties, making the bot configurable per-book without code changes.

**What you'll learn:** Using account/group properties to drive behavior, creating related transactions automatically, working with transaction amounts.

## Exchange Bot

[GitHub](https://github.com/bkper/bkper-exchange-bot)

Converts transaction amounts between Books based on updated exchange rates and calculates realized gains and losses. Demonstrates **multi-book synchronization** — when a transaction is checked in one book, the bot creates corresponding entries in connected books.

**What you'll learn:** Mirroring transactions between books, working with exchange rates, gain/loss calculations, cross-book data flow.

## Portfolio Bot

[GitHub](https://github.com/bkper/bkper-portfolio-bot)

Keeps stocks/bonds instruments book in sync with financial books and calculates realized results using FIFO method. Demonstrates **quantity and instrument tracking** — managing financial instruments with both amounts and quantities.

**What you'll learn:** FIFO accounting patterns, tracking instruments with amounts and quantities, synchronized portfolio management.

## Inventory Bot

[GitHub](https://github.com/bkper/bkper-inventory-bot)

Calculates COGS (Cost of Goods Sold) automatically using FIFO method when inventory items are sold. Demonstrates **inventory management patterns** — tracking purchase and sale quantities to compute accurate costs.

**What you'll learn:** Inventory management patterns, purchase/sale quantity tracking, automatic COGS calculation.

## Subledger Bot

[GitHub](https://github.com/bkper/bkper-subledger-bot)

Manages hierarchical relationships between parent and subsidiary books, mapping accounts and groups across ledger levels. Demonstrates **hierarchical ledger relationships** — keeping consolidated and detailed views in sync.

**What you'll learn:** Parent-child book patterns, account/group mapping between books, consolidated reporting.

## Bkper Sheets

[GitHub](https://github.com/bkper/bkper-sheets)

The Google Sheets Add-on — extends Bkper with custom spreadsheet functions, data import/export, and formula-driven reporting. Demonstrates a full **Google Workspace integration**.

**What you'll learn:** Sheets add-on architecture, custom functions, data synchronization between Bkper and Sheets.