How is self-employment tax calculated?

Self-employment tax is 15.3% of your net self-employment earnings — 12.4% for Social Security and 2.9% for Medicare. You first multiply net earnings by 92.35% (the portion subject to SE tax), then apply 12.4% only up to the Social Security wage base ($168,600 in 2024) and 2.9% Medicare on the full amount with no cap. This is the same federal calculation everywhere, including Idaho.

How does Idaho tax self-employment income?

Idaho does not have a separate self-employment tax. Instead, your net self-employment income flows into Idaho's flat 5.8% individual income tax along with your other income. Idaho conforms to the federal deduction for one-half of self-employment tax, so your Idaho taxable income is reduced by that deductible portion.

Can I deduct half my SE tax?

Yes. The IRS lets you deduct one-half of your self-employment tax as an above-the-line adjustment to income on your federal return, and Idaho conforms. This calculator subtracts that deductible half before applying Idaho's 5.8% rate, which lowers your state tax slightly.

Does the Social Security wage base matter?

Yes, for higher earners. The 12.4% Social Security portion of SE tax only applies to net earnings up to the wage base ($168,600 for 2024). Earnings above that are subject only to the 2.9% Medicare portion. This calculator applies the cap automatically, so very high incomes show a lower effective SE-tax rate.

Is federal income tax included?

No. This tool shows federal self-employment (SE) tax plus Idaho state income tax. Your federal income tax (ordinary brackets on your net business profit) is separate and not included here. Use it to estimate the SE and Idaho portions of your overall tax bill.

Idaho Self-Employment Tax Calculator 2024

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How self-employment tax works in Idaho

When you work for yourself, no employer withholds Social Security and Medicare, so you pay both halves yourself as self-employment (SE) tax — a flat 15.3% federally. Idaho has no separate SE tax; instead your net business profit is taxed under Idaho’s flat 5.8% income tax. The two layers — federal SE tax and Idaho income tax — are what this calculator combines, including the federal deduction for half your SE tax that Idaho also honors.

How it works

The calculation follows the IRS Schedule SE order, then adds Idaho:

se base       = net earnings x 92.35%
social security= min(se base, $168,600) x 12.4%
medicare      = se base x 2.9%
SE tax        = social security + medicare        (effectively 15.3%)
half SE tax   = SE tax / 2                         (deductible)
idaho taxable = net earnings - half SE tax
idaho tax     = idaho taxable x 5.8%
total         = SE tax + idaho tax

The 92.35% factor reflects that the employer-equivalent half of SE tax is excluded from the base, mirroring how an employee’s wages exclude the employer’s payroll contribution.

Example and notes

Net self-employment income of $80,000:

se base        = $80,000 x 0.9235 = $73,880
social security= $73,880 x 0.124  = $9,161.12
medicare       = $73,880 x 0.029  = $2,142.52
SE tax         = $11,303.64
half SE tax    = $5,651.82
idaho taxable  = $80,000 - $5,651.82 = $74,348.18
idaho tax      = $74,348.18 x 0.058  = $4,312.19
total          = $15,615.83

Note: This covers federal SE tax and Idaho’s 5.8% income tax only. It excludes your federal income tax, the Idaho standard deduction (applied separately on Form 40), and any additional Medicare tax for high earners. Use it for planning, not filing.