Young Iraqi war victim Ali Abbas has received an apology from the government department which has now decided to backdate his disability allowance.
Ali lost both his arms in the Iraq war
The Department for Work and Pensions (DWP) earlier told Ali his benefits claim would not start until 21 March.
But the 14-year-old, who lives with his uncle in south-west London, will receive a £2,166 lump payment to cover benefits from 15 September 2004.
Ali lost both his arms in a bombing raid which killed his parents.
A DWP spokesperson said: "A thorough and swift investigation of the Ali Abbas case has now been carried out.
"The investigation finds that though the decision to award Ali Abbas the lower rate of mobility was correct, he should have been receiving payments from 15 September 2004."
He said officials had been in contact with his representatives to arrange for the backdated payment to be made.
Zafar Khan, chairman of the Limbless Association, the organisation which brought Ali to the UK, said: "I am only half happy. I would have been happier if they had addressed the whole issue more sympathetically."
Ali will receive £58.50 a week for help with personal care and £15.55 a week for the mobility part of his disability allowance.
But Mr Khan said Ali, who now has artificial limbs, should receive the higher rate of benefit for mobility help.
Thirteen other members of his family were also killed in the bombing.