Look up an Austrian federal office and its buyer group
Search the office you are billing and you have its buyer group – the order reference without which your e-invoice to the Austrian federal government is rejected. Free, no sign-up, straight from the official list.
The buyer group is your order reference
Without a purchase order you put the 3-character buyer group in the order reference, e.g. K40. With a purchase order, use its 10-digit number — every invoice line then also needs an order position.
Only the office can give you the supplier number
You also need your 8-digit supplier number, e.g. 50012345. The office issues it itself — ask them directly, neither erechnung.gv.at nor we can hand it out.
Store it once instead of looking it up every time
In Nori you link the customer to their federal office: order reference and supplier number are prefilled on every new invoice, the ebInterface document is built on send and filed with the authorities if you want.