F-tax
An approval from Skatteverket that shows you run a business and pay your own preliminary tax and social contributions on what you earn from it. Customers who hire someone with F-tax do not have to deduct tax or pay employer contributions on the payment.
Sole traders are normally approved for F-tax. If you also have a job, you are registered for both, which is called FA-tax. You apply through verksamt.se, the joint service of Skatteverket, Bolagsverket and other agencies, logged in with Swedish e-identification.
The opposite is A-tax, the tax that an employer deducts from your salary.