Change your invoice number and number series
Your own prefix, your own starting number, a new series at the turn of the year: how you set the numbers on invoices for your Shopify orders.
In the app you set the prefix and the next number yourself, separately for invoices, delivery notes and credit notes. A change applies from the next document on. A number already printed on an invoice never changes.
The order number is a different number. It comes from Shopify and is printed on every invoice as well.
In the app
How you set your number series:
Open the app's settings and go to Numbering.
Enter your prefix under Invoice prefix, RE-2026- for example. Up to 16 characters work: letters, digits, hyphen, slash, dot and space.
Enter the number to carry on from under Next invoice number. Coming from another program, that is its next number.
Do the same for delivery notes and credit notes if you want other numbers there. Left alone, they start at LS-1 and GS-1.
Save. The next invoice carries the new number.
The app adds no leading zeros. Prefix RE-2027- and number 1 make RE-2027-1, not RE-2027-0001.
At the turn of the year
The app does not go back to 1 by itself. To count from 1 each year, change the prefix and the next number on 1 January, say from RE-2026- to RE-2027- and 1.
If you reset only the number and keep the prefix, the app runs into a number that already exists. It then creates no document and tells you the number is taken. Pick a new prefix.
German VAT law asks for a sequential number "mit einer oder mehreren Zahlenreihen", with one or more series of digits, issued only once (§ 14 Abs. 4 Satz 1 Nr. 4 UStG). How you split your series is a question for your tax adviser.
Order number and invoice number
Shopify gives each order its number. Under Settings > General you can change its prefix and suffix, #1001 to SHOP-1001 for instance. The count starts at 1001, and Shopify's help says that cannot be changed.
The app gives the invoice its number, in its own series. Every invoice names both numbers, so each invoice leads back to its order.
What the app does not do
A number once issued stays issued. So:
It does not change the number on an invoice already issued.
It deletes no invoice to free a number.
It does not start again at 1 each year by itself.
It does not change the order number in Shopify.
Next
The home page shows orders and invoice numbers side by side. What to do when a number is already taken is on the support page.