George Hilleard, who had learning difficulties, was sent a summons for unpaid council tax of£235.
He had applied for council tax benefit and should have been exempt. But his Jobseekers Allowance was mistakenly stopped and he was sent a court summons from CSL, which handles Southwark's council tax and benefits service.
A statement from the council said: 'Mr Hilleard's death was a tragedy and we are deeply sorry for the distress we caused. We are doing everything in our power to ensure that such a dreadful incident should not happen again.'