Can I change the number of an invoice I have already issued?

No. Issued numbers never change; a new format applies from the next document. See Issuing and numbering.

How do I start invoice numbers from a specific number?

Set the Starting number for a new series, such as a new prefix or a new year. A series that has already started carries on from its last number.

How do I put the year in my invoice numbers?

Choose Year as the Date part. Numbers then read like INV-2026-0001, and the count starts again each 1 January.

Why did my new starting number not take effect?

The series with that prefix and date part has already started, so it continues. The Starting number applies to the next new series.

Can quotations and invoices use the same prefix?

No. Every kind needs its own prefix, and the customer code prefix counts too.

How do I change the customer code prefix?

Under Customer numbering & personal details on the same page, change the Customer code prefix. New accounts take it with five digits, such as C-00001.

What happens when my numbers reach the last one that fits the digits?

The series carries on with one more digit, keeping the same prefix and date part.

Document numbers

Copy for AI

Each kind of document has its own number series, such as INV- for invoices. The Document numbers section decides what those numbers look like. This page is for whoever sets up the company; see Issuing and numbering for when each number is taken.

Before you start

You need System View to see the section and System Edit to change it. Without Edit the section is read-only.
Decide the format first. A change applies from the next document, and numbers already issued never change, so the best time is before the first document of a new year.

Steps

Select System settings in the sidebar, then Company under Organisation.
Scroll to Document numbers. It has one block per kind: Quotation, Invoice, Credit note, Receipt, Purchase order, Delivery order and Service contract. A kind whose module is not switched on for your company has no block.
In the block you want, enter the Prefix, such as INV-.
Choose the Date part: None, Year or Year and month.
Set the Number of digits, from 3 to 9.
Set the Starting number: the first number of a new series.
Check Next number beside the block. It reads Checking… for a moment while easySales works it out.
Select Save in the bar at the bottom of the page.

What happens next

The next document of that kind takes the number shown under Next number. Documents already issued keep their numbers.
With Year, numbers read like INV-2026-0001; with Year and month, like INV-202610-0001. Each new year or month starts a new series at the Starting number.
The change is recorded in the Audit log, with the old and the new values.

Rules to know

Each prefix is its own series, together with its date part. A series that has already started carries on from the number shown, and the Starting number applies to the next new series only. The block then says: This series has already started and continues from the number shown. The starting number applies to the next new series.
Purchase orders and delivery orders always carry on after the highest number any document of that kind already has under that prefix, so a new series never repeats a number, and saving the settings never starts one early.
A series that runs out of digits carries on with one more digit. The prefix and date part stay the same, and the block says: The series has passed the last number that fits its digits, so its numbers are now longer. The prefix and date part stay the same.
A prefix starts with a letter and has at most 16 characters: letters, the digits 1 to 9 and - / .. It cannot contain 0, because a 0 would be read as part of the number, or YY, MM or DD in capitals, because they are read as a date. With a date part, it cannot end in a capital Y. The field tells you what to change.
Two kinds cannot share a prefix, and the customer code prefix counts too. Invoices and draft invoices, and quotations and draft quotations, are kept in the same list, so there neither prefix may begin with the other. A clash stops the save with a message that names the other kind.
The standard numbers, such as INV-10000001, show as the prefix INV-1 with seven digits.
A custom format: a few companies have a format that cannot be shown as separate fields. Its block shows a Custom format tag and the Format, and it keeps working as it is. Select Use standard format to switch to the fields, or Keep custom format to undo that before you save.
Numbers you cannot set: draft invoices (proforma), draft quotations, refunds and deposit forfeitures keep their own numbers.
If Next number reads No free number was found., choose a different number of digits, date part or prefix.
Customer codes are set under Customer numbering & personal details on the same page. New customers are numbered with the Customer code prefix and five digits, for example C-00001. The prefix has up to ten characters: letters and - _ / ., starting with a letter.

Why it works this way

Numbers already issued never change. Your customers, your accountant and the tax authority refer to documents by number. Renumbering an invoice your customer has already filed would break every one of those references, so a new format only applies from the next document.

Two documents never share a number. A number is taken when a document becomes final — an invoice when it is issued, a receipt when it is recorded — and easySales checks that it is free before using it. Anyone checking your books can then trace each number to one document. It is also why purchase orders and delivery orders skip past any number already in use under the prefix.

Two kinds cannot share a prefix. If invoices and credit notes both used INV-, they would compete for the same numbers and a reader could not tell the kinds apart. Refusing a clash when you save keeps every number pointing to exactly one document.

A date part restarts the count for you. With Year or Year and month, each period’s documents start again at the Starting number, so INV-2027-0001 is clearly the first invoice of 2027 and nobody has to reset the series by hand.

Work faster

Let Next number check your work. It shows the exact number the next document will take with the values you have typed, before you save, so a typo in the prefix is caught straight away.
Use a date part instead of resetting each year. Year starts a new series every 1 January with no change on your side. See Issuing and numbering.
Change all kinds in one save. Every block is part of the same page, so you can set invoices, quotations and receipts together and select Save once.
Open the section from the Dashboard. For a new company’s administrator, the Check your document numbers step of Get started with easySales on the Dashboard has Open document numbers, which opens this section directly, and Keep the defaults, which marks the step done.

Examples

Lim & Co wants its invoice numbers to show the year. Its invoices so far run from INV-10000001 to INV-10000042.

Mei Tan opens System settings → Company and scrolls to Document numbers.
In the Invoice block she changes the Prefix to INV-, chooses Year, sets the Number of digits to 4 and leaves the Starting number at 1.
Next number shows INV-2026-0001. She selects Save.

The next invoice Lim & Co issues is INV-2026-0001. The 42 earlier invoices keep their numbers. On 1 January the series starts again at INV-2027-0001.

Carrying on from your old numbering. Suppose Lim & Co had invoiced from a spreadsheet until October 2026, and its last invoice there was LC-2026-0187. Mei sets the Invoice block to Prefix LC-, Year, 4 digits and Starting number 188, and Next number shows LC-2026-0188. After the first invoice is issued, the 2026 series has started, so she sets the Starting number back to 1. The block confirms that the series continues, and LC-2027-0001 will open the new year.

A prefix that clashes. Mei tries C- as the credit note prefix. Lim & Co’s customer codes already use C-, so Save is refused with a message naming the customer code. She uses CN- instead.

Common questions

Can I change the number of an invoice I have already issued? No. Issued numbers never change; a new format applies from the next document. See Issuing and numbering.
How do I start invoice numbers from a specific number? Set the Starting number for a new series, such as a new prefix or a new year. A series that has already started carries on from its last number.
How do I put the year in my invoice numbers? Choose Year as the Date part. Numbers then read like INV-2026-0001, and the count starts again each 1 January.
Why did my new starting number not take effect? The series with that prefix and date part has already started, so it continues. The Starting number applies to the next new series.
Can quotations and invoices use the same prefix? No. Every kind needs its own prefix, and the customer code prefix counts too.
How do I change the customer code prefix? Under Customer numbering & personal details on the same page, change the Customer code prefix. New accounts take it with five digits, such as C-00001.
What happens when my numbers reach the last one that fits the digits? The series carries on with one more digit, keeping the same prefix and date part.