Requirements concerning vouchers

‘Vouchers’ means documents which are used as a basis for the bookkeeping in your accounts.

What are the requirements for vouchers?

This could for example be invoices, time sheets or payment vouchers. The bookkeeping rules use the word ‘documentation’ instead of ‘voucher’. In practice, these terms are used interchangeably.

Specific requirements are imposed regarding the type of information that vouchers must contain. One of the most important requirements is that the documentation must be accurate and complete, and there must be no doubt that the voucher is linked to your business. It is also not permissible to alter documentation once it has been created. Changes to amounts stated on outgoing invoices must for example be made by creating a credit note. There are also a number of requirements regarding different types of vouchers. It is important to comply with the requirements of the bookkeeping rules regarding vouchers, partly so that you can document deductions for expenses and input VAT. You will find all the details in Chapter 5 of the Bookkeeping Regulation.

Bookkeeping Act on documentation of posted information (in Norwegian only)

Bookkeeping Regulation on documentation of posted information (in Norwegian only)

Primary documentation and secondary documentation

The Bookkeeping Act makes a distinction between primary and secondary documentation. Primary documentation is used as a basis for the actual bookkeeping process. Secondary documentation often consists of additional documentation which does not directly lead to any transactions in the accounts. Examples of secondary documentation include sales agreements, order slips and other agreements of importance for the enterprise.

In some cases, secondary documentation can also become primary documentation because the primary documentation does not contain sufficient information. If you send an invoice which states: 'Sale in accordance with agreement', the actual agreement will be considered to be primary documentation and must then be stored for the same period of time as the invoice.


Primary documentation must generally be retained for 5 years. Secondary documentation must be retained for 3.5 years.

Bookkeeping Act on storage (in Norwegian only)


The documentation you create yourself must be in Norwegian, Swedish, Danish or English (e.g. outgoing invoices). As a general rule, there are no requirements regarding the language used on vouchers you receive from others (e.g. incoming invoices), but the authorities may require vouchers in languages other than those referred to above to be translated into one of these languages.

Bookkeeping Act on language requirements (in Norwegian only)

Voucher numbering

Vouchers must be systematised in a way which makes it possible to check that the accounts are complete. Vouchers must be consecutively numbered, without any gaps in the number series. If you have any gaps in the number series, you must explain why. However, you can use several number series for different types of voucher if appropriate. Different types of voucher could for example be incoming invoices, bank vouchers and cash register vouchers.

The Norwegian Tax Administration on requirements regarding the numbering of vouchers (in Norwegian only)

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