Tax returns and tax assessments for petroleum companies

Petroleum companies have a different deadline for the submission for the tax return than other companies. There are additional specific forms that must be submitted as attachments to the tax return. In addition, the petroleum companies must each year reply to a number of standard letters. 

The tax return 

The tax return must be submitted online. The deadline for the submission is 30 April, see section 8-2-3 subsection 1, letter b, of the Tax Administration Regulation. In the case of a submission after the deadline, a daily enforcement fine can be imposed, see section 14-1 of the Tax Administration Act.

If the company wishes to apply for an extension, they must send a substantiated, written application to the Oil Taxation Office by post or email before the submission deadline, see section 8-2-5 of the Regulation to the Tax Administration Act.  

The 2024 income year is the second year with the new tax return. Read more about: 

In addition, we refer to the Tax Administration’s other webpages with general information about the tax return. 

The following forms must be submitted as attachments to the tax return: 

Standard letters 

All companies must reply to the following standard letters, including the new standard letter on § 11 investments:

The following standard letters are to be answered if relevant:

The tax assessment 

For the 2024 income year, the tax assessment notice for companies liable to special tax will be sent out in November 2025. The tax assessment with the settlement is sent online via Altinn. The annual press release with the tax list of companies liable to special tax is published no later than 2 December 2025 at skatteetaten.no, see section 9-7, of the Tax Administration Act. 

The due date for the payment/refund of the difference between paid instalment tax and assessed tax is three weeks after the tax assessment notice has been sent out, see section 10-22, subsection 2, of the Tax Payment Act. Interest on the difference between paid instalment tax and assessed tax will be calculated starting on 1 January 2025 up until the due date. 

Interest on the payment of the tax value of deficits in the taxation basis for the special tax (see section 5, subsection 6, of the Petroleum Taxation Act) and unused uplift (see section 11, subsection 7 of the Petroleum Taxation Act) is calculated in the same way as on tax refunds. Payment is made within three weeks of the tax assessment notice being sent out.

Instalment tax

The offshore companies’ ongoing payments (advance tax) are called instalment tax. The assessment of the instalment tax is based on the information provided by each company regarding the expected income for the year in question. From and including the 2025 income year, the instalment tax must be paid in ten instalments – respectively on 1 August, 1 September, 1 October, 1 November, and 1 December in the income year, and on 1 February, 1 March, 1 April, 1 May, and 1 June in the year following the income year.

It is possible to make larger payments than the assessed amounts. Any additional payments must be divided over three instalments, respectively in the second, third, and fourth instalment affecting the first five instalments, and in the seventh, eighth, and ninth instalment affecting the last five instalments.

The Oil Taxation Office can change the assessed instalment tax up until the due date for the sixth instalment with effect for the last five instalments.

After the ordinary tax assessment, the paid instalment tax is offset against the assessed tax. Underpaid tax must be paid (and overpaid tax refunded) within three weeks after conclusion of the tax assessment. Rules for calculating interest have been determined to prevent companies from profiting from an assessment of the instalment tax that is either too low or too high.