Sequential Invoice Numbers in Shopify: Order Number or Its Own Series?

Your accountant asks for “sequential invoice numbers”, and you look at Shopify: every order already has a number, #1001, #1002, #1003. Is that enough? Sometimes yes. Often, once refunds, cancellations and invoices issued at a later moment come in, the order number and the invoice number need to go their separate ways.

This post explains what Shopify numbers, what EU invoicing rules ask for, and how to set up an invoice series that stays clean. It is a practical guide, not tax advice: check the rules of your country with your accountant.

What Shopify numbers

Shopify gives every order a number. By default, your first order ID has the format #1001, and you can change its prefix or suffix under Settings > General > Order ID format (Shopify help). So #1001 can become SHOP-1001 or 1001-EU.

That number belongs to the order. It is assigned when the order is created, whatever happens to the order next.

What an EU invoice asks for

The European Commission’s VAT invoicing page lists the details a full VAT invoice must carry. The first two are the issue date and a unique number, issued in sequence, that identifies the invoice. Documents that amend an invoice, such as credit notes, must make a specific, unambiguous reference to the initial invoice. The page also notes that specific national rules apply in some Member States. To see those details on an invoice you fill in yourself, the Shopify invoice generator shows a checklist of what an EU or UK VAT invoice still lacks.

In practice, three questions decide whether your order number can serve as the invoice number:

1. Does every order get exactly one invoice? An order cancelled before payment may never get one.
2. Is the invoice issued at the same moment as the order? Many shops issue it at payment or at fulfilment.
3. Do refunds get their own documents? A credit note needs its own number and a reference to the invoice.

If the answers are “yes, yes, no refunds”, the order number may do. For most shops, at least one answer is different.

Two ways to number invoices

	Order name as invoice number	Own invoice series
Example	INV-1001 for order #1001	INV-2026-0001, INV-2026-0002
Easy to match to the order	Yes, same number	Print the order number on the invoice too
Orders without an invoice	Leave a hole in the sequence	Never take a number
Year in the number	Only by editing the order ID prefix by hand	Possible, for example INV-{YYYY}-
Credit notes	Need their own series anyway	Own series, such as CN-0001

Ask your accountant which one they expect. Whatever you choose, apply it from one date onwards and do not switch back and forth.

How to run an invoice series without gaps

A sequence only stays clean if numbers are taken at one moment and never reused. These rules keep it that way:

• Take the number when the invoice is issued, not before. A draft, preview or sample should never consume a number.
• One order, one invoice. Printing the invoice again must give the same document with the same number, not a new one.
• Never reuse or edit. If an invoice is wrong, issue a credit note for it and, if needed, a new invoice. The wrong one stays in the sequence.
• Separate series for credit notes, each one referring to its invoice. Shopify’s refund flow records the refund; the credit note is the document for it. More in how to create a credit note for a Shopify refund.
• Watch concurrency. If two people print at the same time, they must not get the same number. This is easy to get wrong in a spreadsheet.
• Decide what happens at year end. Some businesses start each year with the year in the prefix. Agree on it before 1 January, not after.

Where to start the series

If you switch from order numbers to an own series, or from one tool to another:

1. Pick a start date, ideally the first day of a month or year.
2. Note the last invoice number issued with the old method.
3. Start the new series higher than that, or with a new prefix, so the two can never collide.
4. Tell your accountant the date and both numbers.

Keep what you issued

An invoice is a document you sent, not a view of the order. If the template or the order changes later, the invoice you issued should still download exactly as it was. Keep the PDFs, and make it easy to hand a month of them to your accountant.

Where Paperly: Invoice Order Printer fits

Paperly: Invoice Order Printer numbers and keeps invoices this way.

• Numbering: a running sequence with your prefix, digits and next number, with {YYYY} for the year if you want it, or the order name with a prefix. Credit notes have their own series, and draft orders print as quotes named after the draft, without a number from a series.
• Gapless and stable: every number is issued once; each order gets one invoice and each refund one credit note. Printing again gives the same stored file with the same number, and two people printing at the same time never get the same number.
• When to issue: when you print, or automatically when the order is paid or fulfilled.
• Kept for your accountant: every issued invoice and credit note is stored unchanged for 10 years, with a monthly export of the PDFs and a CSV list.
• EU details: your VAT number, the buyer’s company and VAT number from Shopify, VAT per rate and notes such as reverse charge, in 23 languages.

It does not calculate tax, and an issued invoice cannot be edited. Check the invoice rules that apply to your business. See Paperly: Invoice Order Printer for the details.

FAQ

Can I use the Shopify order number as the invoice number? You can, if every order gets exactly one invoice and your accountant accepts it. Orders without an invoice leave holes in the sequence, and refunds still need credit notes with their own numbers.

Can I change Shopify’s order numbers? You can change the prefix and suffix of the order ID under Settings > General. The number itself counts up from your first order.

Do credit notes need their own number? A credit note is a document in its own right; EU rules require it to refer clearly to the invoice it amends. Most businesses give credit notes their own series.

Should the year be in the invoice number? It is a common choice, not a general EU rule. Ask your accountant what your country expects.