# Invoices API
This directory contains documentation for working with invoices in the Harvest API v2:
1. [Invoice Item Categories](01_invoice_item_categories.md)
- Managing invoice item categories
- Category types and properties
- CRUD operations
2. [Invoice Messages](02_invoice_messages.md)
- Sending invoice messages
- Message templates
- State changes via messages
- Email notifications
3. [Invoice Payments](03_invoice_payments.md)
- Recording payments
- Payment options
- Payment management
- Thank you messages
4. [Invoices](04_invoices.md)
- Main invoice operations
- Creating invoices (free-form and from time/expenses)
- Managing invoice states
- Line items management
- Invoice properties and attributes