Can I use Treasury bills to hold my cash safely?

Yes — short-term Treasury bills (T-bills) are one of the safest places to park cash, backed by the full faith and credit of the U.S. government with no FDIC cap. They come in maturities from a few weeks to a year, you buy them at a discount and receive face value at maturity, and the interest is exempt from state and local income tax — a real benefit in high-tax states. You can buy them directly through TreasuryDirect or inside a brokerage account, and you can build a ladder so some matures regularly. The trade-off versus a savings account is liquidity: your money is committed until maturity (or you'd sell on the secondary market at whatever price), so T-bills suit the deeper layers of cash, not the first dollars you'd grab in an emergency. Keep your truly instant-access reserve in savings.