Accurate estimation of improper payments “is key to understanding the extent of the problem and to developing effective corrective actions,” GAO has said, but the six agencies and 10 programs it sampled–which collectively reported outlays of over $2.5 trillion in 2017–used varying approaches in making those estimates.
The sample included for example OPM’s payments to federal retirees along with Medicare claims, military pay and administration of the earned income tax credit. Regarding the first, GAO said that OPM’s does not estimate overpayments but rather uses actual overpayments identified in IG reports and in other ways. GAO said that “may not reflect significant risks of improper payment in the program, calling into question the improper payment estimate and its usefulness for developing effective corrective actions.”
GAO also said that:
* several of the agencies reported using processes designed specifically to estimate improper payments, whereas others reported leveraging existing reviews;
* agencies varied in the treatment of insufficient documentation, both in identifying and in reporting the root causes of improper payments; and
* the age of the data used in producing fiscal 2017 estimates ranged from calendar year 2013 to fiscal year 2017.