In Sweden, taxes are almost always withheld at the time of salary payment, because employers are obliged to deduct tax from your salary before you are paid.
<aside> 💡 Employed PhD students have a normal salary and normal taxes.
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You can calculate your taxes here:
Räkna ut din skatt - Ekonomifakta
Everyone who has been working in Sweden during the whole or part of the previous should submit a tax return (Inkomstdeklaration 1). This income tax return form is sent by the Swedish Tax Agency in April to all those obliged to submit a tax return.
<aside> 💡 You have an obligation to declare taxes every year. Usually, it is in the first week of May. Please refer to the video by Swedish Tax Agency.
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For more information about taxes in Sweden
<aside> 💡 Those who had 90% of their income for a calendar year from their employment as a PhD student, can get "grundavdrag" during their tax declaration.
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Experience from a collegue:
I would like to mention, that those who had 90% of their income that calendar year from their employment as a PhD student, can get "grundavdrag" during their tax declaration. In my case I was unemployment before my PhD studies began. I started in May. As a foreigner, all my income that year were from my employment as PhD student, but I was taxed the normal rate (if I had worked the whole year). When you ask for grundavdrag your salary will be averaged, and thus be lower than what you were taxed for, resulting in a big tax return (6000SEK in my case.)