You moved to London. California may not have noticed.

The Franchise Tax Board says you are a resident if you are in California for other than a temporary or transitory purpose, or if you are domiciled in California but outside it for a temporary or transitory purpose. The state taxes residents on income from all sources.

Domicile is the place you intend to return to.

The FTB page on residency status states both tests.

No. A move abroad ends California residency only if it is not temporary or transitory, which is a question of facts rather than of distance. Someone on a two-year secondment who keeps a house, a car and a voter registration in California may still be a resident.

So the plane ticket proves very little on its own.

What proves the move is everything else that went with it.

The same logic runs the other way. A genuine, permanent move with the ties cut usually ends California tax residency even without a contract.

It is a rule for people leaving under an employment contract. FTB Publication 1031 says a California domiciliary who is outside the state under an employment-related contract for an uninterrupted period of at least 546 consecutive days is treated as a nonresident.

Return visits totaling no more than 45 days in a tax year covered by the contract count as temporary.

The rule also covers a spouse who accompanies you for the same period.

Keep a copy of the contract. It is the document the whole rule rests on.

Publication 1031 lists two exceptions. It does not apply if you have intangible income over $200,000 in any tax year during which the contract is in effect, or if the principal purpose of the absence is to avoid personal income tax.

Intangible income means things like interest, dividends and gains.

In our practice the $200,000 test catches people who sell a large stock position the year they leave.

Time a large sale for before the contract starts or after it ends, and California tax on the gain becomes a separate, smaller question.

Then there is no safe harbor, and your residency turns on the facts. The FTB says the underlying theory is that you are a resident where you have the closest connections, and that the strength of the ties matters more than their number.

No single factor decides it.

The FTB's Publication 1031 lists the factors in detail.

That makes the facts you create in the first year abroad unusually important. They are the record the FTB will read.

Publication 1031 gives a partial list. It covers time spent in California versus elsewhere, where your spouse and children live, your principal residence, the state that issued your driver's license, where your vehicles are registered and where you are registered to vote.

It also covers bank accounts, professional licenses, doctors, advisers and social ties.

Each tie left in California weakens the case that you moved.

Strength matters more than number. A family home you still live in outweighs a dozen minor accounts.

Yes, and it runs against you if you stay. The FTB presumes you are a California resident for any tax year in which you spend more than nine months in the state. For someone genuinely living in London, that presumption rarely matters.

It matters more for people who split the year.

Keep a day count if you travel back often.

Remember that the presumption and the safe harbor are separate rules. Meeting one does not settle the other.

It matters a great deal, because the location of your spouse and children sits near the top of the FTB's list. A family that stays in California while one partner works abroad makes the absence look temporary.

The safe harbor covers an accompanying spouse, not one who stays behind.

So families who move together have a far simpler case than families who split.

Children's schools count as well, since they show where the family has settled.

If you remain a resident, yes, because the state taxes residents on income from all sources. As a nonresident, you pay only on California-source income, such as rent from a California property.

That single status question therefore decides almost everything.

It is also why the evidence of your move deserves as much care as the move itself.

Not at state level. The Schedule CA instructions tell you to enter the federal foreign earned income and housing exclusion as a positive adjustment, which adds the excluded income back for California. Federally excluded wages become taxable wages again for a resident.

So the relief that zeroes your federal tax does nothing at state level.

The adjustment appears in the Schedule CA instructions.

No. California's credit for taxes paid to other jurisdictions tells you not to include taxes paid to any foreign country. A resident taxed by Britain on a British salary therefore pays state tax on the same income with no credit.

That is genuine double taxation, and nothing in the treaty fixes it.

The exclusion is in the Schedule S instructions.

More than most people expect, because nothing offsets it. A resident earning a British salary pays British income tax, then state income tax on the same wages, with the federal exclusion added back and no credit for the British tax.

Federal tax may be zero at the same time, which makes the state bill easy to miss.

In our practice, clients who discover this late face several years of state returns at once.

On a professional salary the state's graduated rates add up quickly, so the sums can be large.

Because it only covers federal tax. Article 2 of the US-UK treaty lists the United States taxes it applies to as the federal income taxes imposed by the Internal Revenue Code. Only the non-discrimination article reaches state and local taxes.

So treaty relief and foreign tax credits stop at the federal return.

The IRS page for the UK treaty documents links the convention.

Rent from it stays California-source income, so as a nonresident you usually still file a California return to report it. A later sale of the property is California-source as well, whatever country you live in by then.

Keeping the house also counts as a tie in the residency analysis.

We cover the wider picture in keeping your American house after you move.

You are usually a part-year resident. California tax then applies to worldwide income for the part of the year you were resident, and only to California-source income after the move date you can prove.

So the move date needs evidence behind it, such as a flight record, a new lease and the start date of your new job.

Income received around that date needs care, particularly bonuses and share awards earned partly before you left.

Documents that show the move was real and permanent. Keep your foreign lease or purchase, your employment contract, proof of selling or letting your California home, and confirmation that you surrendered your license and changed your voter registration.

Add a day log for every visit back.

These papers answer the FTB's questions far better than a statement of intent.

Scan them and store them with your tax files. Paper kept in a California storage unit helps nobody.

Most of this is best done in the months around the move, while the evidence is easy to create.

Take a software engineer who moves from San Jose to London on a three-year contract. She sells her condo, surrenders her California license and spends 20 days back a year.

She sits inside the safe harbor, so California treats her as a nonresident. Had she kept the condo and a Bay Area voter registration without a contract, the facts could have pointed the other way.

In that case her British salary would face state tax with no credit for British tax. This example is illustrative, not advice.

Her colleague, who kept his house and family in Palo Alto, had a much harder conversation with the FTB.

Short visits are fine, and the safe harbor expressly allows up to 45 days a year under a qualifying contract. Longer stays, a return to the same home or a new California job all point back toward residency.

Moving back permanently makes you a resident again from the date you return.

Plan the timing of any return with a tax year in mind.

A return in January rather than December can keep a whole tax year clean.

First, assuming a federal foreign address ends California residency.

Second, relying on the exclusion to shelter California tax. The state adds it back.

Third, selling a large stock position during the contract and breaking the $200,000 limit.

Fourth, keeping every tie in place just in case, which is exactly what makes the move look temporary.

Fifth, leaving a spouse and children in California while claiming a clean break. The FTB treats family location as a strong tie.

We look at your California position before you move, when the ties are still easy to cut, and file the part-year return alongside your US federal return. Our guide to filing a US return from abroad covers the federal side.

We also review whether any California-source income keeps you filing afterwards.

This article is general information, not personal tax advice. Talk to us before you leave.