Additional advance tax
If you realise that you’ll have underpaid tax, you may wish to consider paying additional advance tax. Then, you do not have to pay any additional interest on the underpaid tax.
You’ll have underpaid tax when your calculated tax exceeds the withholding tax and advance tax. You’ll have to pay underpaid tax within three weeks after the tax assessment is sent out.
Underpaid tax of more than NOK 1,000 will be split into two instalments. The deadline for the second instalment is five weeks after the first due date. Underpaid tax of less than NOK 100 does not need to be paid.
To avoid paying interest on underpaid tax, you can pay additional advance tax as a self-employed person by 31 May. If the 31 May is a weekend or public holiday, the deadline is the first business day after.
How do I pay additional advance tax?
Use the KID number and account number that you received with your tax return. As a self-employed person, you have until 31 May to pay additional advance tax.