Payment for my T-bills debited from my bank checking account Thursday

The payment for the 28-day T-bills that I purchased in my new account at TreasuryDirect was in fact debited from my bank checking account on Thursday, although I was unable to see the debit until today.

It remains unclear whether I can safely roll the T-bills over in August without needed a spare $1,000 in cash in my bank checking account to cover for the next debit which will be covered by the credit for this month's maturing T-bills. Even if the debit and credit occur at the same instant, the bank may require a day before the credit is actually posted against the account. I simply do not know, but I'll probably have an extra $1,000 sitting in the account at the beginning of August anyway. Maybe I need to switch to the Zero-Percent C of I to eliminate this uncertainty, anxiety, and confusion.

-- Jack Krupansky