Work in Idaho, Live in Washington: How Taxes Work

Reciprocity

Do Idaho and Washington Have a Tax Reciprocity Agreement?

No. Reciprocity agreements let a worker pay tax only to the home state when the two states have signed a pact. Washington has no personal income tax, so it has nothing to swap with Idaho, and no reciprocity has ever been established between the two states. If you live in Washington and cross the border to work in Idaho, Idaho taxes the wages you earn for services performed inside Idaho.

Washington's Department of Revenue confirms that Washington does not currently have an individual income tax. That means as a Washington resident you file no state resident return, no matter where your wages come from. Your only state filing obligation is with Idaho, and only for the portion of your compensation that Idaho treats as Idaho source income.

The Lewiston to Clarkston corridor and the Coeur d'Alene to Spokane corridor are two of the busiest daily crossings on the Idaho, Washington border. Workers in aerospace, healthcare, logistics, and hospitality routinely commute from one state to the other, so this filing situation is common along the Snake River and the Palouse.

Filing Obligations

Which Tax Returns Do I File as a Washington Resident Working in Idaho?

Form 43 is the Idaho income tax return for nonresidents with income from Idaho sources. Report your federal adjusted gross income in Column A and your Idaho source income in Column B. Idaho computes tax on the full federal figure, then multiplies by the Idaho percentage from line 38 to determine what portion applies to you.

Nonresidents of Idaho must file if their total gross income from Idaho sources is more than $2,500 for the year. If your Idaho source wages fall below that threshold, you generally do not have an Idaho filing requirement. If your employer withheld Idaho tax on those small wages, you may still want to file to claim a refund. Form 43 doubles as an original return or an amended return, and you do not need to attach a copy of your federal return.

Source Allocation

How Is Idaho Source Income Calculated for a Cross-Border Worker?

Idaho source income is income from transactions or activities that take place in Idaho, or from property located in Idaho. For wage earners, the state uses a workday ratio to isolate the Idaho portion of a paycheck when the employee splits time between states for the same employer.

The formula is simple. Divide Idaho work days by total work days, then multiply by total compensation from that employer. Idaho work days are the total days you worked in Idaho for a particular employer during the year. Total work days are the total days you worked for that employer both in and outside Idaho. You count only days you provided personal services, not vacation, holidays, or sick leave. A five day work week is approximately 260 work days per year before time off is subtracted.

Example: if you worked 220 total days for the year and 187 of them were physically in Idaho, your Idaho percentage is 85%. Multiply 85% by your annual wages to get the Idaho source amount that flows into Column B of Form 43. Keep a calendar with location entries for every workday, because Idaho may ask you to substantiate the ratio during a residency audit.

Rate and Threshold

What Rate Does Idaho Apply and What Is the Filing Threshold?

Idaho moved to a single flat individual income tax rate. For tax year 2025 the rate is 5.3% on Idaho taxable income, reduced from 5.695% in 2024 by House Bill 40. Idaho has not yet published its 2026 rate at the time of writing, so use the current 5.3% figure until the Idaho State Tax Commission announces a change. Your nonresident tax equals the Idaho tax on your Idaho source amount, computed after Idaho standard or itemized deductions apportioned by the Idaho percentage.

The nonresident filing threshold is $2,500 of Idaho source gross income for the year. This is a gross income test, not a taxable income test, so bonuses, tips, and other Idaho earned compensation count toward it. Idaho income tax returns follow the federal calendar and are due April 15 of the following year. Idaho grants an automatic six month filing extension if at least 80% of the current year tax or 100% of the prior year tax was paid by the original due date, but interest still accrues on any balance not paid by April 15.

Employer Withholding

How Does My Employer Handle Idaho Withholding?

If your employer has an Idaho location, Idaho income tax withholding applies to wages you earn for services performed inside Idaho. Your W-2 should show Idaho wages in Box 16 and Idaho income tax withheld in Box 17. If you split days between an Idaho worksite and a Washington worksite for the same employer, the employer should withhold on the Idaho share only, not on days spent working in Washington.

If your employer is based in Washington and you occasionally travel to Idaho for work, that employer is generally not required to withhold Idaho tax on the Idaho days. Idaho cannot force a Washington company that has no Idaho presence to run Idaho withholding, though many multi-state payroll providers will do so voluntarily. If nothing is withheld to Idaho, you should make quarterly estimated tax payments to Idaho on Form 51 to avoid an underpayment penalty. Estimated payment due dates track the federal schedule (April 15, June 15, September 15, and January 15 of the following year).

Worked Example: WA Resident Earning $80,000 with 187 Idaho Work Days

Single filer, one employer, 220 total work days, 2025 rates

Remote Work

What If I Work Remotely from Washington for an Idaho Employer?

Idaho does not currently apply a convenience of the employer rule to nonresident remote workers. If you live in Washington and work from a Washington home office for an Idaho employer, the days you spend physically working outside Idaho are not Idaho source income. Only the days you are physically inside Idaho generate Idaho source wages for a nonresident.

Hybrid schedules make the day count material. If you go into the Idaho office two days a week and work from Washington three days a week, roughly 40% of your annual work days are in Idaho, and only that portion flows onto Form 43 Column B. Keep a written work location log, because Idaho auditors will look for corroborating evidence such as timecards, badge swipes, and expense records if they question the allocation. Tell your payroll department in writing about your split, so withholding matches the days actually worked in Idaho and you avoid a large refund or a large balance at filing time.

Mid-Year Move

What If I Moved Between Washington and Idaho During the Year?

If you moved into Idaho during the year, you file Form 43 as a part-year resident. During the resident months, Idaho taxes all of your income from every source. During the nonresident months, Idaho taxes only your Idaho source income. Form 43 handles both scenarios by checking the part-year resident box on the residency section and entering the number of full months you lived in Idaho.

If you moved out of Idaho to Washington, the same part-year approach applies for the Idaho resident months, and there is no Washington resident return to file. Keep dated records of your move (a signed lease, utility activation, a driver's license change, and a voter registration update) because Idaho residency depends on domicile, and the state can look at intent as well as physical presence. Both an existing Idaho employer and a new Washington employer should be notified of your address change so withholding matches your current situation.

Local Taxes

Are There Any Local Income Taxes in This Corridor?

Neither Idaho nor Washington imposes a local, county, or municipal income tax on wages. Your total state and local wage tax bill in this commute corridor is simply the Idaho state income tax on your Idaho source amount. That is a much simpler picture than corridors such as MD to PA, where a Pennsylvania local Earned Income Tax layer applies, or Ohio and Kentucky, where city and school district income taxes can stack on top of the state rate.

Washington workers who cross into Idaho should still consider Washington's other payroll obligations, such as the state's Paid Family and Medical Leave premium and the WA Cares Fund long-term care premium. Those are Washington state payroll deductions, not income taxes, and they do not affect the Idaho calculation. Review your paystub each January to confirm which taxes and premiums apply based on where you live and where you physically work.