Why did my pay change?
Enter a before and an after — a different salary, state, filing status or dependent count — and see every line that moved, ranked by size, with the causes this tool can actually prove called out separately from the ones it can't.
What this deliberately does not do
It does not read your actual pay stubs, and it does not know what you earned last year — there is no prior-year tax data behind this site to compare against, so a real state rate revision or a real year-over-year change is outside what it can attribute. It also does not model 401(k), HSA, or other pre-tax benefit inputs on either side; both scenarios are priced the same simplified way the state comparison and reciprocity pair pages already use, so the two sides stay comparable to each other even if neither matches your own paycheck exactly.
How to read the causes list
Only four things ever appear there, because only four things are provable from two scenarios without guessing: gross pay itself changing, a federal bracket crossed, the Social Security wage base crossed, or the state or filing status changing. A line in the ranked table with no cause listed above it still really changed — it just was not one this tool can explain with certainty, and saying so honestly is the point.
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