The worst day in a contractor's financial year shouldn't be April 15th. But for most self-employed tradespeople, it is — because they get a bill for money they didn't plan for, using funds they already spent.
This guide explains why self-employment taxes are higher than most expect, how to calculate what you owe, and how to build an automatic set-aside system that makes tax season just another day on the calendar.
When you work for an employer, they pay half of your Social Security and Medicare taxes (7.65%). You pay the other half through payroll deductions and never see it.
Self-employed, you pay both halves — the full 15.3% SE tax on 92.35% of your net profit, plus regular federal income tax on top. A contractor with $70,000 net profit can easily owe $18,000–$22,000 in total federal taxes. If you didn't plan for that number, you've likely already spent it.
Step 1: Estimate your net profit (revenue minus all business deductions).
Step 2: Calculate SE tax: net profit × 0.9235 × 0.153.
Step 3: Deduct 50% of your SE tax from income before calculating income tax.
Step 4: Apply your federal bracket rate to the adjusted figure.
Step 5: (SE tax + income tax) ÷ 4 = your quarterly payment.
Practical shortcut: Set aside 28–32% of every payment you receive into a dedicated tax savings account and make quarterly payments from it.
Q1 (Jan–Mar income): Due April 15, 2026
Q2 (Apr–May income): Due June 16, 2026
Q3 (Jun–Aug income): Due September 15, 2026
Q4 (Sep–Dec income): Due January 15, 2027
Missing these deadlines doesn't just defer your bill — the IRS charges underpayment penalties. Pay on time even if your estimate isn't 100% precise. You can true up at filing.
Open a separate savings account and label it "TAX." Every time money hits your business checking, immediately transfer your set-aside percentage to this account.
Treat it as money that was never yours. It belongs to the IRS from the moment the client pays you. Automate the transfer so willpower is never required.
Home office: $5/sqft up to 300 sqft = max $1,500 using the simplified method.
Vehicle mileage: Track every business mile at the IRS standard rate. A mileage log in your glove box costs nothing and is worth thousands in deductions.
Section 179: Most tools and equipment under $2,500 can be fully expensed in the purchase year.
Health insurance premiums: 100% deductible if you're self-paying and have no employer plan available through a spouse.
SEP-IRA contributions: Contribute up to 25% of net profit — and deduct every dollar. At higher income levels this is a massive tax reducer.
The Trades Money Kit Tax Estimator automatically calculates your SE tax, income tax, total quarterly payment, and exact IRS due dates. Enter your numbers once — it handles all the math.
Get the Tax Estimator — $47 Bundle