Scotland Yard's review of the Madeleine McCann case is expected to cost nearly £2 million in its first year.
Detectives from the Metropolitan Police's Homicide and Serious Crime Command are carrying out a re-examination of the original investigation into the girl's disappearance in Portugal in May 2007.
Since beginning work last May, the British officers have travelled to Spain and Portugal to pursue lines of inquiry.
Scotland Yard said it expected to recover £1.9 million from the Home Office for the cost of the Madeleine case review up to the end of March this year, of which it has already claimed for £800,000.
Madeleine was nearly four when she went missing from her family's holiday flat in Praia da Luz in the Algarve on May 3 2007 as her parents Kate and Gerry dined with friends nearby.
Portuguese detectives, helped by officers from Leicestershire Police, carried out a massive investigation into her disappearance.
But the official inquiry was formally shelved in July 2008 and since then no police force has been actively looking for the missing child.
Scotland Yard's review of the case, called Operation Grange, was launched after a request from Home Secretary Theresa May supported by Prime Minister David Cameron.
Critics have argued that the decision to bring in Met detectives to review the evidence about what happened to Madeleine has undermined the force's independence and diverted resources from other crime victims.