The agency is encouraging taxpayers to make use of the online service.
"My tip to all those declaring is to do so on the internet. It is simpler and therefore avoids mistakes, for example if you have sold shares or a property," said the tax agency's director-general Ingemar Hansson in a statement.
In order to declare on the internet, users must have a digital identification certificate installed on their computer.
A new addition to this year's declaration is that more than 500,000 Swedes have made use of the ROT and RUT tax deductions for work done on or in their homes.
The tax agency will this year post 7,388,461 declaration documents, which should have reached postboxes by April 15th. The deadline for declarations is May 3rd.
Closer checks will be conducted on items such as travel to and from work, as well as the sale of shares and property.