Does your state require estimated tax payments?

If your state has an income tax, almost certainly yes. The part that surprises people is that states do not copy the federal rules. The thresholds, the safe harbor percentages, and sometimes the payment schedule itself are different. Paying the IRS on time does nothing for your state bill.

The easy case is a state with no income tax

Nine states currently have no tax on wage or self-employment income: Alaska, Florida, Nevada, New Hampshire, South Dakota, Tennessee, Texas, Washington, and Wyoming. Live in one of those and your quarterly obligation is federal only. (One wrinkle is that Washington taxes large capital gains through a separate excise, so a big investment year there can still owe state tax.)

Everywhere else, same idea with different rules

The idea is the same as the federal system. If you will owe more than some threshold at filing, the state wants installments during the year, and a safe harbor based on last year's tax protects you. But every piece can differ:

• The trigger threshold is often lower than the federal $1,000, so a state obligation can exist even when the federal one does not.
• Safe harbor percentages vary, and some states offer no high-earner discount or set their own.
• The schedule itself can differ. California is the famous example. Its installments are weighted 30%, 40%, 0%, 30%, not four equal payments. Pay California in even quarters and you are underpaid in the spring even though the total is right.
• Each state sets its own penalty interest rate and changes it on its own schedule.

The practical consequence is that your federal payments do not count toward the state. Your state's number needs its own calculation on its own schedule, paid through the state's own portal (most have a Direct Pay equivalent).

What to check for your state

1. Does my state have an income tax at all?
2. What is the owe-at-filing threshold that triggers estimated payments?
3. What safe harbor does it honor, and at what percentage of last year's tax?
4. Are the four installments equal, or weighted like California's?
5. Where do I pay online, and do the due dates match the federal ones?

Source: state revenue department guidance current at publication