FastBill Invoicing

FastBill is an invoicing and bookkeeping service for German freelancers and small businesses. This connector reads customers, outgoing invoices, expenses (Kosteneinträge) and revenues (Einnahmen) through the FastBill API 1.0. Every tool is read-only.

Getting credentials

1. Sign in at my.fastbill.com, click your name in the top right corner, open Einstellungen (Settings) and scroll to the bottom: the API-Key is shown there. Put it in FASTBILL_API_KEY.
2. Put the e-mail address you sign in with in FASTBILL_EMAIL. Both are sent together as HTTP Basic authentication.

FastBill Automatic, the subscription billing product, uses a different API host and is not covered by these tools.

How the API works: every tool POSTs a JSON body to one URL, https://my.fastbill.com/api/1.0/api.php, naming a SERVICE such as invoice.get. The answer repeats the request under REQUEST and puts the data under RESPONSE, e.g. RESPONSE.CUSTOMERS[] or RESPONSE.INVOICES[]. Problems are reported in RESPONSE.ERRORS: read it before concluding that a list is empty.

Filters and fields: TERM on fastbill_list_customers searches organization, first and last name, address, ZIP code, e-mail and tags. Invoices and expenses can be narrowed by MONTH and YEAR (FastBill marks these filters as deprecated but still accepts them), invoices also by CUSTOMER_ID. fastbill_get_invoice takes the internal INVOICE_ID, not the printed invoice number. On invoices, TYPE is outgoing, draft or credit (credit note) and STATE is draft, unpaid, overdue, paid or canceled; leave drafts, credit notes and cancelled invoices out when adding up revenue. SUB_TOTAL is net, VAT_TOTAL the VAT, TOTAL gross. Dates are YYYY-MM-DD.

Pagination and limits: without LIMIT, FastBill returns 10 entries; the maximum is 100 per call. Page with OFFSET (0, 100, 200 …) until fewer than LIMIT entries come back. The number of calls per hour depends on the plan: Solo 50, Solo-Plus 100, Pro 500, Premium 1000. Fetch 100 entries per call rather than many small pages.

Cloud reachability: my.fastbill.com is publicly reachable over HTTPS.