“Charges will be brought by January 23rd, 2018 at the latest,” the authority said in a statement on Thursday.
Uzbek national Akilov, who confessed to driving a truck down Stockholm's Drottninggatan and into pedestrians last April, is the only suspect in the case.
It will have around 150 plaintiffs including victims and family members of those impacted by the attack.
Five people were killed and several more injured in the April 7th attack. Police apprehended Akilov later that day after he fled the scene.
As The Local has previously reported, the trial is expected to start no later than early February.