Although the Treasury can and does hold cash and a special deposit account at the Fed (TGA account), these assets do not count in any of the aggregates. So in essence, money paid in taxes paid to the Federal Government (Treasury) is excluded from the money supply. To counter this, the government created the Treasury Tax and Loan (TT&L) program in which any receipts above a certain threshold are redeposited in private banks. The idea is that tax receipts won't decrease the amount of reserves in the banking system. The TT&L accounts, while demand deposits, do not count toward M1 or any other aggregate either.