The expenses must be attributable to the sickness/debility. You cannot claim an allowance for expenses you would have incurred had you been healthy. If the sickness has resulted in your expenses being greater than they would otherwise have been, you can still claim an allowance for the added expenses. Consideration is therefore only given to the added expenses that are due to your sickness, etc. However, the requirement for a causal link also entails a requirement for the sickness/debility and the expense to be sufficiently closely linked.
You can for example claim an allowance for medical expenses (personal contributions to the public health service), medicines, expenses for suitable medical aids, added expenses due to the sickness, e.g. as a result of special dietary requirements and expenses for supervision, care and essential help around the home.
You can also claim an allowance for your expenses for private treatment, care or stays at an institution or private health practice outside the Norwegian public health and social services sector, but no corresponding service must be offered by the Norwegian public health service in such cases. In addition, the health authorities must assess whether the private health service concerned is professionally competent and appropriate. In such cases, Sections 6-83 (1) and (2) must both be met in order for you to be entitled to the special allowance.
You can read more about this and other aspects of the special allowance for major sickness expenses in the guidance to the tax return and in Tax ABC under the topic "Special allowance - sickness or debility".