FastBill API Documentation

All documented changes to the FastBill API reference in reverse chronological order.

03.07.2026

Customer

Added New field GLN in actions customer.get / create / update

02.06.2026

Invoice

Changed VAT_CASE in invoice.create / update and recurring.create now only accepts defined VAT cases

08.05.2026

Invoice

Fixed Service period in invoice.create now defaults to invoice date when no period is specified

27.04.2026

Invoice

Changed VAT_CASE slugs in invoice.create / update and recurring.create now use external identifiers (e.g. small_business_regulation instead of small_business)

22.04.2026

Customer

Changed Field BANK_BIC in customer.create is no longer required

14.04.2026

Invoice

Added New fields CUSTOMER_ACCOUNTING_NOTE, CONTRACT_REFERENCE, CUSTOMER_ORDER_REFERENCE and ORDER_REFERENCE in invoice.get / create / update

27.11.2025

Customer

Changed Field COMMENT in customer.create / update, invoice.create / update, expense.create and revenue.create now has a maximum length of 1000 characters

18.11.2025

Invoice

Added Filter STATE in invoice.get now additionally supports values canceled and issued
Changed Status value created in invoice.get response has been renamed to issued

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