To log in to Kivra, you need to have a Mobile BankID. If you are temporarily without a Mobile BankID but have access to another type of e-identification, you can instead log in directly to the Swedish Tax Agency (Skatteverket).
On Skatteverket's "My Pages" (Mina sidor), you can find your tax return as a PDF starting from March 6.
Read more about the tax return at Skatteverket here.