Numeric Series of Invoices and Expenses
MyInvoiceOnline.co.uk fills in the document number automatically based on your active number sequence. The numbering is set separately for each type of document, so invoices, expenses and proforma invoices each have their own independent sequence.
How numbering works for documents
In the app, documents are split into two groups. Tax documents cover invoices and expenses. Proforma invoices sit under Other documents – a proforma invoice isn't a tax document, so it has its own numbering, separate from your invoices.
Quickly changing the number when issuing a document
If you want to use a different number for a particular document than the sequence suggests, overwrite the document number field. The app will ask whether you want to use the number once or update the settings.
Number sequence settings in My Account
You can also change the numbering format outside of issuing a document. Go to My Account and choose Number Sequences. The settings are split into three tabs – Invoices, Expenses and Proforma invoices – so you can set each sequence separately.
For each sequence you pick one of three preset formats, or create your own.
Abbreviations for creating number sequences
You build the numbering format from variables:
{YYYY} or {YY} – the current year (YYYY = 2026, YY = 26)
{MM} – the current month
{NNNN} – the sequential counter with leading zeros; adjust the number of zeros by the number of N letters (e.g. {NN} for a two-digit number)
Preset formats
Format 1 – Year, month and number: {YYYY}{MM}{NNNN}. The first invoice in April 2026 will be numbered 2026040001.
Format 2 – Year and number: {YYYY}{NNNN}. The first invoice of 2026 will be numbered 20260001.
Format 3 – Sequential number only: {NNNN}. After invoice 0001 comes 0002.
Creating your own format
If none of the preset options suit you, build your own format from the variables above plus any text:
{YYYY}/{NN} → the first document of 2026 will be 2026/01
INV{YYYY}/{MM}/{NN} → the first issued invoice in April 2026 will be INV2026/04/01
You can fine-tune the sequential number for any format in the Sequence Number field.
Saving and switching to a new year
Once you've changed the format, click Save and you can start invoicing straight away.
Need help with the setup? Write to us at [email protected].
Do invoices and proforma invoices share the same numbering?
No. Each document type has its own independent number sequence – you set invoices, expenses and proforma invoices separately.
Why do proforma invoices have their own sequence?
A proforma invoice isn't a tax document, so it's numbered separately from invoices and expenses.
Where do I set up the number sequences?
In My Account → Number Sequences, or directly when issuing a document by overwriting the number field.
Can I add text to the document number?
Yes. You can type any text into the format, for example INV or PF before the variables.
What happens to the numbering at the start of a new year?
For formats with a year variable, the app automatically updates the year and continues numbering according to your chosen format.
What if I enter a number that already exists?
The app shows a duplicate warning so you don't issue two documents with the same number.
