Determination engine

Which state do you actually withhold in?

Reciprocity, convenience-of-the-employer, nonresident thresholds and unemployment localization, applied together to one employee's facts. Every answer cites the state source it came from.

Withhold Idaho income tax.

The work state does not tax these wages, so the residence state governs.

Income tax withheld to

Idaho

Flat 5.3%

Employee certificate

None required

No state withholding allowance certificate applies.

Unemployment insurance

Utah

Localized under factor 1: Localization.

Reciprocal agreement

Utah has no reciprocal agreements.

✓

Below the Utah nonresident threshold

Utah does not require nonresident withholding until the employee exceeds 20 working days in the state. You entered 0. Per Utah Pub 14: do not withhold Utah tax for a nonresident employee who (1) has no other sources of Utah income, (2) works in Utah for 20 days or less, and (3) is a resident of a state that either has no income tax or provides a substantially similar exclusion for nonresidents (mutuality requirement). COST phrases this as 'more than 21 days'; the Pub 14 language ('20 days or less') is used here.

Track this, because it flips mid-year

Once the threshold is crossed, most states require withholding on all in-state wages for the year, not just the excess. Set an alert well before the limit.

Idaho also taxes this income, with a credit

The residence state taxes worldwide income. The employee claims a credit on the Idaho return for tax paid to Utah, which prevents true double taxation but usually still leaves a balance if Idaho's rate is higher. Some employers withhold for both states; many withhold only for Utah and let the employee manage the difference.

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Employer registrations you will need

Idaho — Income tax withholding: Idaho State Tax Commission
Utah — Unemployment insurance: Utah Department of Workforce Services

Utah profile Idaho profile Full write-up for this pair

Change the inputs

Withholding determination

Answer six questions. The result is a shareable link, so you can paste it into a ticket or an email.

Employee lives inState of residence

Work is performed inWhere the employee physically sits

Employer is based inWhere the work is directed from

Days in the work stateThis calendar year, leave blank if unknown

Wages from work-state daysUS dollars, leave blank if unknown

Arrangement Works remotely rather than at an employer location Remote work is an employer necessity, not employee preference

Run a whole roster instead

This is a determination aid, not advice. StateSide encodes published state rules and applies them mechanically to the facts you enter. It does not know your entity structure, your nexus history, your equity compensation, or the dozens of exceptions that turn a clean rule into a judgement call. Every determination cites the state source it came from — verify against that source, and take anything consequential to a payroll tax professional before you act on it.