How do I handle estimated taxes for both federal and my state at the same time?

Most states with an income tax run their own pay-as-you-go system that mirrors the federal one, with separate vouchers, deadlines, and safe-harbor rules. You generally cannot combine them; you pay the IRS through Form 1040-ES or IRS Direct Pay and your state through its own portal. Deadlines often align with the federal dates but not always, so check your state's schedule. States with no income tax, such as Texas, Florida, and Washington, skip this entirely, though a few levy a separate business or franchise tax. Set aside money for both by estimating your combined effective rate, then split the payments. Missing state estimates triggers state penalties independent of anything federal.