If it would like to take on a major case, it must go cap-in-hand and ask the Treasury for extra cash.
According to a report by the BBC, the SFO is currently in talks with Treasury to change this funding structure.
David Green, SFO director-general, told the BBC that, while the ultimate decision on funding lies with the Treasury, he has never been hampered from pursuing a case because of a lack of funding.
The funding talks show a marked difference between the government and the SFO from May last year, when prime minister Theresa May attempted to abolish the agency and hand its responsibilities over the National Crime Agency.
In September 2017, this plan was abandoned by May.
The SFO has a wide-ranging remit that has seen it investigate fraud cases at home and abroad.
One recent case of note, in early March, was the SFO calling for a retrial of three former Tesco executives accused of fraud and false accounting.
Further, in November 2017, the SFO charged the boss of Harlequin, a defunct property Caribbean group, with three counts of fraud.