Idaho self-employment tax calculator

The first year of self-employment usually contains one unpleasant discovery: a tax that never appeared on a payslip. As an employee, Social Security and Medicare cost 7.65% of wages because the employer pays a matching 7.65%. Work for yourself and both halves are yours, which is 15.3% before a dollar of income tax.

The tool above computes that payroll piece exactly, and is careful to say what it leaves out, because the quarterly figure it shows is only part of what you need to send the IRS.

What does self-employment tax actually cost?

15.3% of 92.35% of net profit, split into 12.4% for Social Security and 2.9% for Medicare. The Social Security half stops once combined wages and self-employment income reach $184,500 for 2026. The Medicare half never stops. On $85,000 of net profit the total is $12,010.

The two inputs are Net self-employment profit and W-2 wages this year.

How this calculator works

Three steps.

First it reduces the profit. Only 92.35% of net profit is subject to the tax, because the notional employer half is deducted before the tax is worked out. On $85,000 that gives $78,497.50, shown as $78,498.

Second it splits the rate. The self-employment rate of 15.3% less two times the 1.45% Medicare rate leaves 12.4% for Social Security. The engine derives both from the published FICA figures rather than hardcoding them, so the prose and the tool cannot drift apart.

Third it applies the wage base. Social Security is charged on the smaller of that 92.35% figure and whatever is left of the $184,500 wage base after your W-2 wages. Medicare is charged on the whole 92.35% figure with no cap.

Two derived lines follow. The deductible half is exactly half the total, and it reduces your income tax rather than this tax. The quarterly figure is the total divided by four, which is a set-aside prompt rather than a computed estimated payment.

What does a worked example look like?

A freelancer with $85,000 of net profit on Schedule C and no W-2 job.

That $12,010 is 14.13% of the $85,000 headline profit, not 15.3%, because of the 92.35% reduction. It is also before any income tax at all.

What happens if I also have a job?

W-2 wages consume the Social Security wage base first, so a day job can wipe out most of the 12.4% portion. The Medicare portion is untouched.

In the right-hand column only $34,500 of the wage base is left, so 12.4% applies to $34,500 rather than to $78,498. That is why the field exists and why leaving it at zero when you have a salaried job overstates your bill by thousands.

How does the bill scale with profit?

Almost linearly until the wage base bites, then it flattens sharply.

The $200,000 row is the interesting one. Its 92.35% figure is $184,700, just past the $184,500 wage base, so Social Security is capped at 12.4% of $184,500 and every further dollar of profit costs only 2.9%. That is the point at which a marginal dollar of self-employment income gets meaningfully cheaper.

What counts as net profit?

Gross revenue minus ordinary and necessary business expenses, which is the bottom line of Schedule C. It is not what you paid yourself, and it is not the balance in the business account at the end of the year. Draws from a sole proprietorship or a single-member LLC are not a deductible expense, so taking less out of the business does not reduce this tax by a dollar.

Expenses that do reduce it include software subscriptions, professional fees, business insurance, advertising, the business portion of a vehicle, a qualifying home office, contractor payments and the employer side of any payroll you run. Health insurance premiums for the self-employed are deducted against income tax rather than against this profit figure, so they do not lower the self-employment tax.

The practical consequence is that bookkeeping discipline moves this number directly. Every legitimate expense left uncaptured costs you 15.3% on top of whatever your income tax rate is, which is why a shoebox of receipts is expensive rather than merely untidy.

How do I use it, step by step?

1. Enter Net self-employment profit: revenue minus deductible business expenses, which is the bottom line of Schedule C. Not revenue, and not your draws.
2. Enter W-2 wages this year if you also hold a job. Use gross wages, not net pay.
3. Read the headline as payroll tax only.
4. Note the deductible half. It comes off your income before income tax is worked out, so it is worth roughly your marginal rate in cash.
5. Add your own income tax estimate on top of the quarterly figure before you send anything to the IRS. The income tax calculator does the federal side.
6. Move the combined amount into a separate account on the day the money arrives, not at the end of the quarter.

Common mistakes

Sending the quarterly figure as your estimated payment. The $3,003 in the worked example covers self-employment tax alone. Federal income tax on the same $85,000 of profit is a separate and usually larger sum, and state income tax may be a third. Underpaying triggers a penalty even if you settle up in April.

Entering revenue instead of profit. The field is net profit. A freelancer with $85,000 of revenue and $20,000 of expenses has $65,000 of profit and a materially smaller bill. Deduct first, then enter.

Forgetting to enter W-2 wages. The tool cannot know about your day job. With $150,000 of wages already paid, the correct figure in the example above is $6,554 rather than $12,010, a difference of $5,456.

Treating the deductible half as a credit. It is a deduction, not a credit. Half of $12,010 is $6,005 of income removed from the income tax calculation, which saves you tax at your marginal rate, so perhaps $1,321 at a 22% rate rather than $6,005.

Assuming an LLC changes the number. A single-member LLC taxed as a sole proprietorship pays exactly the same self-employment tax. The entity type changes liability and paperwork, and the cost of running one is a separate question from the tax on the profit.

Where this tool stops

It computes payroll tax only, with no state field and no income tax. It does apply the additional 0.9% Medicare surcharge, but against the single-filer threshold of $200,000. Filing jointly the surcharge starts at $250,000, so a joint filer between the two figures will see a surcharge line that is too high.

It does not model the qualified business income deduction, which can reduce the income tax on the same profit substantially, and it does not model an S corporation election, where a reasonable salary is subject to FICA and the remaining distribution is not. For anyone consistently profitable above roughly the level in the example, that election is the main lever available and it needs an accountant rather than a calculator.

It also does not handle partnerships with guaranteed payments, church employee income, or farm optional methods, all of which have their own rules on Schedule SE.

Before your next quarterly payment

• Reconcile your books so the profit figure is real, not an estimate of an estimate
• Add your income tax estimate to the self-employment tax before paying
• Check whether your state requires its own quarterly estimated payments
• Enter W-2 wages from any job, including a spouse job if you file jointly and the wages are yours
• Confirm the payment deadline for the quarter with the IRS estimated taxes page
• Keep the set-aside in a separate account, ideally one that pays interest until the money is due
• Review whether an S corporation election is worth modelling with an accountant

The Social Security wage base rises most Januaries with average wages, which moves the point where the 12.4% portion stops. The 15.3% rate itself has been stable for decades. The FICA explainer carries the current base, and the IRS estimated tax page carries the payment dates, which shift when a due date falls on a weekend or holiday.