> For clean Markdown of any page, append .md to the page URL.
> For a complete documentation index, see https://developers.gappify.com/api-reference/inbound-to-gappify/3/llms.txt.
> For AI client integration (Claude Code, Cursor, etc.), connect to the MCP server at https://developers.gappify.com/_mcp/server.

# 3. Invoices


## API Docs

- 3. Invoices [Create a new or update existing Invoices entries.](https://developers.gappify.com/api-reference/inbound-to-gappify/3/post.md)
- 3. Invoices [Get a list of Invoices](https://developers.gappify.com/api-reference/inbound-to-gappify/3/get.md)
- 3. Invoices [Retrieve Invoices by ID](https://developers.gappify.com/api-reference/inbound-to-gappify/3/get-by-id.md)

## OpenAPI Specification

The raw OpenAPI 3.1 specification for this API is available at:
- [OpenAPI JSON](https://developers.gappify.com/openapi.json)
- [OpenAPI YAML](https://developers.gappify.com/openapi.yaml)