# F-sąskaita API

> Create and manage invoices and expenses for a Lithuanian business programmatically. REST, JSON, bearer tokens, webhooks.

The F-sąskaita API lets you issue invoices, record expenses and download documents for the business you run in [app.fsaskaita.lt](https://app.fsaskaita.lt). It is a small REST API: JSON in, JSON out, bearer tokens scoped to one business.

```
https://app.fsaskaita.lt/api
```

## What you can do

| Resource | Operations |
|---|---|
| Invoices | list, create, read, update, delete, download PDF |
| Expenses | list, create with a file, read, update, replace file, delete, download file |
| Profile | read the business behind the token |
| Currencies | list accepted currency codes |
| Webhooks | receive `invoice.*` and `expense.*` events at your HTTPS endpoint |

## Start here

1. [Authentication](/guides/authentication): create a Business token and make the first request.
2. [Invoices](/guides/invoices): the invoice model, numbering and the create request.
3. [Expenses](/guides/expenses): multipart uploads and file replacement.
4. [Webhooks](/guides/webhooks): subscribe, verify the signature, handle retries.
5. [Conventions](/guides/conventions): pagination, errors, rate limits, dates and money.

The [Reference](/reference) covers every endpoint. The specification itself is at [`/openapi.json`](/openapi.json).

## For AI agents

Read [`/llms.txt`](/llms.txt) for an index of every page, [`/llms-full.txt`](/llms-full.txt) for the full text, and the [agent page](/agents) for a compact description of how to integrate.

Instructions for agents: https://docs.fsaskaita.lt/agents/prompt.md

## Plan requirement

API access and webhooks are included in the Premium plan. On other plans the token and webhook settings are not available in the app.