How an Idaho paycheck works
Idaho taxes wages at a single flat rate, but only above a threshold. The employer annualises your pay, and anything up to the threshold for your filing status is withheld at nothing at all. Above it, the flat rate applies to the excess and the result is rounded to the nearest whole dollar. There are no brackets to climb.
The threshold is not an Idaho invention. It tracks the federal standard deduction for the same status, so when Congress moves that figure, Idaho withholding moves with it.
Federal income tax withholding
Federal withholding annualises the wage, subtracts the standard deduction that matches the filing status on Form W-4 Step 1, applies the graduated schedule for that status, and deducts the dependent credit from Step 3. This page models a W-4 with Steps 2 and 4 left blank: one job, no spouse income, no other income, no extra withholding. Above the income limit for the status, the dependent credit tapers by a set amount for every thousand dollars of excess rather than disappearing at a cliff.
Social Security and Medicare
Social Security applies a flat rate to wages up to an annual ceiling that is re-indexed each year, so it stops partway through the year for a high earner. Medicare applies to every dollar, and above a fixed wage threshold the employer withholds the Additional Medicare tax on the excess, with no employer match and no regard for filing status.
Two columns, and head of household is not one of them
The percentage computation table has exactly two columns: single persons, which the heading says expressly includes head of household, and married persons, whose threshold is double. So ticking head of household on this page changes your federal withholding but leaves the Idaho line where it was. A married employee gets the wider nil band regardless of whether their spouse works, which means a two-income couple can be under-withheld if both claim it.
The tables changed partway through the year
Idaho is candid that it revises its withholding tables when it needs to, usually partway into a year rather than on 1 January, and the version behind this page carries a mid-year revision date. The Tax Commission's instruction to employers is to start using a new table going forward and not to correct withholding already taken earlier in the year.
The practical consequence is that a payslip from January and one from December can both be correct and still disagree with each other. This page uses the table currently in force, so it will match your later payslips rather than your earlier ones. The annual return settles the difference.
Idaho withholding allowances are now worth nothing
Before the table is applied, Idaho lets an employee subtract an allowance for each Idaho withholding allowance claimed on Form ID W-4, taken from a separate table tied to the state child tax credit. That credit has expired, and the Tax Commission now says the allowance amount is zero.
So claiming allowances on Form ID W-4 no longer lowers Idaho withholding, and the figure on this page is the same however many you claim. If the legislature brings the credit back, the allowance will have a value again and this page will ask for it.
Local income tax
No Idaho county or city taxes wages. Boise, Meridian and Idaho Falls all have the same payroll deductions as anywhere else in the state.
What the employer pays on top
The employer matches Social Security and Medicare and pays federal unemployment tax at its net rate. Idaho unemployment insurance is charged to the employer at a rate set from its own claims record on a state wage base, so it is left out. There is no employee-side state levy in Idaho: no disability insurance, no paid family leave premium.
What this calculator assumes
The figure models a salaried employee paid evenly across the year with a standard Form W-4 and no pre-tax deductions. It leaves out:
- Pre-tax contributions such as a 401(k), health premiums, HSA or flexible spending accounts, which reduce the wages subject to income tax and often to FICA.
- Extra withholding requested on the federal or state certificate, and the W-4 Step 2 and Step 4 adjustments.
- Bonuses and other supplemental wages, which are withheld at the flat rate when paid separately.
- Employer-side state unemployment insurance, which is priced per employer, and any federal unemployment credit reduction.
- Employees outside the normal Social Security system, such as some public-sector staff and certain visa holders.
Withholding versus your final tax bill
Withholding is a prepayment. The annual returns, federal and state, replace these standard assumptions with your real situation: itemised deductions, other income, and credits payroll knows nothing about. One job usually produces a refund; two jobs, a working spouse or investment income often produce a balance due.