Side Income Tax Calculator — What You Owe on Extra Earnings
By Sanjeet Singh, CPA
You already have a day job. You're earning extra money on the side. This calculator shows how that changes your tax bill.
Filing Info
Income
$0.70/mile (2025 IRS rate)
Enter your income to see your tax estimate.
Got a W-2 job and earned extra money on the side? You need to know the incremental tax cost — what does each additional dollar cost you? That number is different from someone who's self-employed full-time, and this page explains why.
The key insight: if you already have a W-2 job, your side income falls into your *marginal tax bracket*, which is higher than someone with no other income.
The Incremental Cost of Side Income
Let's say you earn $65,000 from your W-2 job and make an additional $5,000 from occasional consulting or tutoring. That $5,000 doesn't get taxed at the lowest bracket — it gets added to your existing $65,000, so it's taxed at your *marginal* rate (roughly 22% federal for single filers in 2026).
Here's the incremental cost breakdown for different W-2 base salaries:
| W-2 Income | Side Income | SE Tax | Federal Tax | State Tax | Total Tax on Side Income | % of Side Income | |---|---|---|---|---|---|---| | $40,000 | $5,000 | $707 | $550 | $250 | $1,507 | 30% | | $65,000 | $5,000 | $707 | $1,100 | $250 | $2,057 | 41% | | $100,000 | $5,000 | $707 | $1,100 | $350 | $2,157 | 43% |
Notice how the tax percentage *increases* as your W-2 income grows? That's because you're in a higher tax bracket. The same $5,000 side income costs 30% in taxes if you earn $40K at your day job, but 43% if you earn $100K.
What Counts as Taxable Side Income?
Not all side money is taxable income. Here's the distinction:
- Taxable: Freelancing, consulting, tutoring, gig work, selling products (at a profit), rental income, affiliate income - Non-taxable: Selling personal items at a loss, birthday gifts, insurance reimbursements, loan proceeds, prizes from contests you didn't enter - Gray area: Selling handmade crafts or vintage items — if you do it repeatedly to make a profit, it's taxable. One-off sales are typically not.
If you made $2,000 tutoring, that's fully taxable. If you sold old furniture for $500 and made $200 profit, that $200 is taxable as miscellaneous income (not SE income).
When Do You File It?
Side income goes on Schedule C (if you're self-employed) or Schedule 1 (if it's miscellaneous income). Self-employment income (consulting, freelancing, gig work) goes on Schedule C and triggers self-employment tax. Other income types go on Schedule 1.
If your net self-employment income exceeds $400, you must pay quarterly estimated taxes — the same as a full-time freelancer. The deadlines are April 15, June 15, September 15, and January 15.
Strategies to Reduce Side Income Taxes
- Claim business expenses: If it's self-employment income, every dollar in deductions saves you 30–43% in taxes (depending on your bracket). Mileage, software, equipment, home office — these add up. - Health insurance deduction: If self-employed, deduct 100% of health insurance premiums from income (before calculating SE tax). - SEP-IRA or Solo 401(k): Contribute up to 25% of net self-employment income ($3,650 limit in 2026 for Solo 401k, higher for SEP-IRA) and deduct it. - Time your payments: Bunching side income into high-expense years reduces marginal tax impact.
Calculate your side income tax impact →
Related Reading
- Freelance income tax guide - How to deduct home office - SEP-IRA vs Solo 401k
Frequently Asked Questions
Is selling personal items taxable?
Generally, no — if you sell something for less than you paid for it, there's no taxable gain. Selling old furniture, clothes, or electronics at a loss is not taxable. However, if you sell an item for a profit (e.g., flipping vintage furniture you bought for $100 and sold for $400), the $300 profit is taxable. If you regularly buy and resell items as a business, all profits are subject to self-employment tax.
I made $2,000 tutoring on the side. How much tax do I owe?
Roughly $280 in self-employment tax plus income tax at your marginal bracket. If you earn $65,000 at your W-2 job, your marginal bracket is 22% federal, so the extra $2,000 costs roughly $440 in federal tax. Add state tax (roughly 5%, or $100) and you're looking at $720–$850 total tax on that $2,000. Your net income is roughly $1,150–$1,280. Remember: if you have business expenses (supplies, mileage), you deduct those before calculating tax.
Do I need to report side income if no one sent me a 1099?
Yes. You must report all self-employment income above $400, whether or not you received a 1099-NEC or 1099-MISC. The 1099 is just a courtesy from the payer — if it's missing, you're still responsible for reporting. Not reporting it is tax fraud, and the IRS catches this through cross-checks. File accurately even without a 1099.
Related Calculators
Need the full picture?
Combine W-2, freelance, and rental income into one complete tax estimate with our full calculator.