OLAF investigates fraudulent use of EU funds. In 2014 it received 1417 allegations of fraud, the highest number since it was established in 1999, it said in a statement.
OLAF has cut the length of its 'selection phase', when it chooses whether to investigate an allegation, to an average of two months, and the average direction of an investigation to 21 months, it said.
In 2014 234 investigations were opened, and 250 concluded, while 397 recommendations were made for financial, judicial and disciplinary action to be taken.
Director Giovanni Kessler said: "OLAF's mission is to detect, investigate and stop fraud involving EU funds. Our work delivers concrete results. It ensures that EU taxpayers' money is used for the purpose for which it was originally intended, creating jobs and growth in Europe."
"The results of our investigative activity in 2014 confirm the strong performance reported by OLAF last year. We have concentrated on those cases where our intervention is most needed and can bring real added value – on complex investigations in areas such as structural funds, customs, smuggling, trade and external aid. These cases will contribute to substantial recoveries to the EU budget," Kessler said.
The €901 million will "progressively return to the EU budget and help fund other projects", OLAF said.
This is the second year in a row where OLAF has reported record results – in April 2014, it reported that it opened 58% more investigations in 2013 than it did in 2009, following a reorganisation of its working methods.
In 2013, it saw a 35% increase in the number of reports of alleged fraud compared to 2009, it said.
OLAF is charged with protecting the financial interests of the European Union by investigating fraud, corruption and any other illegal activities and by investigating matters of serious concern relating to the discharge of professional duties by EU institutions, bodies and staff which might result in criminal or disciplinary measures. It has no judicial or disciplinary powers and can not oblige national prosecutors to act on its disciplinary recommendations.
The changes affecting its working practices come as the European Commission moves forward with the establishment of the European Public Prosecutor's Office (EPPO) which would investigate fraudulent use of EU tax-payer's money. The Commission has said that the role of OLAF will change when this is in place.
OLAF will remain responsible for administrative investigations in areas that don't fall under the competence of the European Public Prosecutor. These include irregularities affecting the EU's financial interests, and serious misconduct or crimes committed by EU staff without a financial impact, the Commission said.
EU fraud or other crimes affecting the financial interests of the EU will be under the exclusive competence of the European Public Prosecutor's Office once it is established.
OLAF has contributed to negotiations on setting up the EPPO throughout 2014, it said, "as well as those on the directive on the protection of the EU's financial interests and to legislation enhancing effective customs cooperation".