Phaup worked at the U.S. Congressional Office for 30 years where he specialized in budget concepts and budgetary accounting. His professional objective has been to develop and retain practices that would improve the match between budget and economic costs, especially for complex transactions including credit, insurance, lease-purchases, deferred compensation, and implied guarantees. He contributed to the development of the Federal Credit Reform Act of 1990, which changed the budgetary accounting of federal direct and guaranteed loans from cash-basis to accrual. He wrote several Congressional Budget Office reports about the inadequacies of current budgeting for government-sponsored enterprises, including Fannie Mae and Freddie Mac, and the Pension Benefit Guaranty Corporation. Phaup also served as Director, Federal Budget Reform Initiative, The Pew Charitable Trusts from July 2009 to December 2010.