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To model a move, add a residency change to your plan. It names a state, and optionally a locality, with a start and an optional end. CoastMath taxes each year as a full-year resident of one state: the state that applies after any move during that year. The one exception is a move between California and a state without an income tax. In that case, California taxes only the wages earned while you lived there.
- In Plan details, set State and Local income tax to where you live now. This is the starting residence.
- Under Residency timeline, choose + Add residency change and pick the new State.
- Set Start: At milestone ties the move to an event such as retirement, and In year fixes a calendar year.
- Leave End as Indefinite for a permanent move. For a stay that ends, set an end milestone or year.
- Choose the new residence’s Local income tax, or leave it at None.
- Choose Save residency changes. Unlike the rest of Plan details, the timeline doesn’t save automatically.
- In year starts on January 1 of that year. An In year end includes all of that year.
- A start milestone applies for the whole year it occurs in. An end milestone stops the row for the whole year it occurs in.
- When rows overlap, the one higher in the list wins.
- When no row applies, the starting state from Plan details applies. A return home therefore needs only an end on the away row.
Move from New York to Florida in July 2026
New York income tax for 2026 is $0. Florida applies to the whole year, including wages from January to June.
Stay in New York all of 2026
New York income tax is $6,039.75 on the same $120,000 salary for a single filer.
When a year includes California and one of Alaska, Florida, Nevada, New Hampshire, South Dakota, Tennessee, Texas or Wyoming, California tax is prorated. CoastMath computes the year’s tax on all income at California rates. It then keeps California’s share: the wages earned while you lived in California, taken month by month from the move’s month. Other income, such as pensions, withdrawals and gains, goes with the state that applies to the year.
| California tax on the full year’s income | $7,067.98 | |
|---|---|---|
| × | Share of wages earned in CaliforniaJuly to December | 50.0% |
| = | California income tax for 2026 | $3,533.99 |
No exemption credits claimed. Moving from California to Texas on the same date gives the same result.
The proration applies only to W-2 wages. It isn’t used when the year also has any of these: pre-tax contributions such as 401(k) deferrals or deductible IRA contributions, self-employment income, an HSA, head of household status, California dependents, tax history entered for the first year, or capital losses. In those cases the whole year stays with one state, as described above, and OverviewModel assumptions and limitations gives the reason. A move tied to a milestone without a fixed date, such as reaching financial independence, counts from January.
A residency change affects state and local income tax only. How each state and locality is taxed is in State and local income tax. Housing, living costs and health coverage stay as entered. A state’s pension and retirement-income exclusion follows the state of each year, so moving from New York to Pennsylvania replaces the $20,000 New York limit with Pennsylvania’s full exclusion from the year of the move. Tie the rest to the same milestone if they change with the move; see Milestones and event timing and Selling a home or property. California SDI and Washington payroll premiums follow the work coverage periods you enter, not your residence.