Source: Board of Governors of the Federal Reserve System (US)  

Release: H.4.1 Factors Affecting Reserve Balances  

Units:  Billions of U.S. Dollars, Not Seasonally Adjusted

Frequency:  Weekly, Ending Wednesday

Notes:

This account is the primary operational account of the U.S. Treasury at the Federal Reserve. Virtually all U.S. government disbursements are made from this account. Some tax receipts, primarily individual and other tax payments made directly to the Treasury, are deposited in this account, and it is also used to collect funds from sales of Treasury debt.