I should add that congress does not allow the Pres to keep money in the checking account forever. The appropriations have limiting dates. If you haven't obligated the funds they are unavailable. The most severe limitation is on 1 year funds that expire at the end of the FY (Sepember). That results in cash crunches that usually start around June - July. When you add in first the continuing resolution funded at FY12 levels, not the FY13 budget, and then sequestration, that's why you see the Chinese firedrill going on now.