Two taxes on the same dollar, capped differently

Published 2026-10-18 · Last reviewed 2026-10-18

One tax is printed at the bottom of a receipt and paid in the same minute; the other is claimed months later on a schedule, and only if it beats the standard deduction. Sales tax and the state and local tax deduction both take a bite out of the same dollar, but they are computed in opposite directions and capped by different rules. This page prices a purchase and then a SALT worksheet, with both engines building the numbers.

Sales tax rides on top of the price

A combined rate is just the state, county, city and special-district rates added together, and every layer is charged on the same pre-tax base. On a $100 purchase at 6.00 percent state, 1.00 percent county and 0.50 percent city, the combined rate is 7.5 percent and the tax is $7.50, for a total of $107.50. The layers do not compound on each other - they add - which is why a receipt can list four lines that sum to one percentage.

A tax-inclusive price holds less tax than the rate suggests

Run the same rate backwards and a subtlety appears. If $107.50 already includes the tax, the tax inside it is $7.50. The rate is charged on the pre-tax price, while a share computed from the total divides by a bigger base, so at this rate the tax is 6.98 percent of what the customer hands over - smaller than the 7.5 percent on the shelf tag. Reading a tax-inclusive price as if the rate applied to the total overstates the tax every time.

Every layer is charged on the same base

SALT is one deduction with a cap, a phase-down and a floor

The state and local tax deduction runs the other way. It is not charged on a price; it is a line on Schedule A, and only worth taking if your itemized total beats the standard deduction. On its own it is capped at $40,400 for most filers, cut by 30 percent of modified AGI above $505,000, and never allowed below $10,000. Those three pieces - a cap, a phase-down and a floor - are what make the number move.

Take $60,000 of state and local taxes paid. At a low income of $200,000 the limit is the full $40,400, so $40,400 deducts. At $600,000 of MAGI, the excess over $505,000 is $95,000, and 30 percent of that is $28,500 off the cap, leaving $11,900 - still above the $10,000 floor. So the same $60,000of taxes deducts $40,400 at the lower income and only $11,900 at the higher one, without a dollar more being paid.

Where these numbers come from

• IRS Publication 505 (2026) and the Schedule A instructions. The $40,400 cap, the $505,000 phase-out start, the 30 percent reduction and the $10,000 floor are the published 2026 amounts the SALT calculator uses.
• State and local rates are the filer's own input. A combined rate is only meaningful for a specific address, so the calculator takes the layers you enter and charges every one on the same pre-tax base - no compounding, no invented jurisdiction.
• The reverse direction is a separate step. It backs the tax out of a tax-inclusive total as gross x rate / (100 + rate), which is why the 6.98 percent share is smaller than the 7.5 percent rate.

What this guide does not cover

It prices one purchase at one combined rate and one SALT worksheet. It does not model item-specific exemptions, food and clothing rules, use tax on out-of-state purchases, or the interaction of the SALT line with the rest of Schedule A - the deduction here only matters if itemizing beats the standard deduction overall. It also leaves out the state income tax you may owe on the same income, the married-filing-separately caps, and any state-level deduction that differs from the federal one. A real address can carry a special district rate this page never sees.

Reconcile a receipt in the Sales Tax Calculator, or cap your deduction in the State and Local Tax (SALT) Deduction Calculator.

Estimates only - not financial, tax or legal advice, and it does not predict how the IRS will treat a particular return. Read the full disclaimer.