Supporting documents (bilag)

A bilag, or supporting document, is documentation of a financial transaction, for example receipts, invoices, timesheets or other relevant documents. The Norwegian Bookkeeping Act often uses the term dokumentasjon (documentation), but in practice bilag and dokumentasjon are used interchangeably. Supporting documents serve as evidence for the entries in the accounts, and are decisive for ensuring correct and reliable bookkeeping.

General requirements for supporting documents

For a supporting document to be valid and meet the requirements of the Norwegian Bookkeeping Act, it must contain correct and complete information about the transaction. Some important points:

• Accuracy and completeness: The document must give an accurate description of the transaction, including the date, the amount and the parties involved. There must be no doubt that the document belongs to your business.
• Unaltered documentation: Supporting documents must not be changed after they have been created. If a mistake has been made, such as an incorrect invoice, a credit note must be issued rather than the original invoice being altered.
• Numbering: Supporting documents must be numbered consecutively, so that it is possible to check the completeness of the accounts. Gaps in the number series should be avoided, but if one arises there must be an explanation of why.
• Retention: Businesses must retain supporting documents for at least 5 years. (This is the retention period under Norwegian rules.)

Why do supporting documents matter?

Supporting documents are necessary in order to ensure that the accounts are correct and auditable. They provide evidence for each entry and help maintain trust in the business's financial reporting. Without valid supporting documents it can become difficult to prove that the transactions are genuine, which can create problems in an audit or a tax inspection.

Examples of supporting documents

• Receipt: Evidence of the purchase of goods or services.
• Invoices: Documentation of a sale or purchase between businesses.
• Timesheets: An overview of hours worked, as the basis for wage payments.
• Bank statements: Evidence of receipts into and payments out of the business's bank account.