Your State May Not Follow the Federal Deductions

Everything on this site describes federal tax. A federal deduction reduces the income the federal government taxes. Whether it also reduces the income your state taxes is a separate question with a separate answer, and in some states the answer is no.

This catches people because the federal return is where you enter everything. It feels like one system. It is not — it is one form feeding two authorities that do not have to agree.

How states connect to federal rules

Most states that tax income start their calculation from a federal figure — usually federal adjusted gross income or federal taxable income — and then apply their own additions and subtractions. That starting point is what makes conformity a question at all.

States generally take one of a few approaches:

• Rolling conformity. The state automatically follows the federal code as it currently stands. A federal change flows through unless the state passes something to stop it.
• Static or fixed-date conformity. The state follows the federal code as it existed on a specific date. A federal change made after that date does not apply until the state updates the date — which usually requires legislation.
• Selective conformity. The state adopts some federal provisions and specifically rejects others, item by item.

A state can also conform to the starting figure but decouple from a specific deduction, adding it back on the state return. That is a common way to accept a federal simplification without accepting its cost to state revenue.

Where the new deductions land in that structure

This is the structural detail that matters most. The tips, overtime, senior and car loan interest deductions are claimed on Schedule 1-A and reach the federal return after adjusted gross income — they reduce taxable income, not AGI.

So for a state that starts from federal AGI, these deductions do not flow through automatically at all. The number the state imports was computed before the deduction was applied. For a state that starts from federal taxable income, they may flow through — subject to whatever additions the state then makes.

SALT sits differently again. It is an itemized deduction, and states that allow itemizing typically have their own rules about which itemized deductions they permit — many disallow the deduction for state taxes on a state return, for the obvious reason.

What this means practically

Three situations, and it is worth knowing which one you are in.

• No state income tax. The question does not arise. The federal deduction is the whole benefit.
• State tax, no conformity for these provisions. Your state taxable income is unchanged. The federal saving is the whole saving, and any estimate that assumed a state benefit is too high.
• State tax with conformity. The deduction reduces state taxable income as well, and the total saving is larger than the federal figure alone.

Our calculators report federal figures only. That is a deliberate choice — a state estimate we could not keep current would be worse than no estimate.

How to check your own state

We do not publish a state-by-state list, because conformity positions change with each legislative session and a stale list is actively misleading. The reliable route is short:

1. Go to your state's department of revenue or taxation website — the official one, not a summary site.
2. Look for the current year's individual income tax instructions, and within them the section on additions to income or federal conformity.
3. Search that document for the provision by name. If the state has decoupled, there will be an addition line for it.
4. If nothing appears, the state may simply be silent because it starts from AGI and the question never arises.

If you use tax software, it generally applies your state's current position for you. That is one of the better arguments for using it in a year when the federal rules have changed this much.

Quick answers

• Does my state have to follow federal law? No. States set their own income tax rules and choose how closely to track the federal code.
• Will my state decide later in the year? Possibly. States sometimes update conformity dates retroactively, which is why checking close to filing is better than checking early.
• I work in one state and live in another. Then two sets of state rules are in play. This is a case for a preparer rather than a guide.
• Does this affect my withholding? State withholding follows state rules. If your state does not conform, nothing about your state withholding should change on account of these federal deductions.

For the federal side of the calculation, the Total Savings Estimator combines the Schedule 1-A provisions from one set of inputs. Treat the result as the federal figure and add your state answer to it separately.