Self-employment tax is 15.3% of your net earnings. That's 12.4% for Social Security (up to $168,600 in 2026) and 2.9% for Medicare, with no cap. Add federal income tax at your marginal rate and you're looking at a combined effective rate of 25-35% on every dollar of profit.
W-2 employees never see this because their employer pays half and payroll withholds the rest. As a freelancer, you see all of it, four times a year, when the IRS expects a check via Form 1040-ES.
Here's how to calculate your Q2 estimated payment (due June 16, 2026) from scratch. The same method applies to every quarter.
Gross revenue for the quarter minus deductible business expenses. If you earned $28,000 in April and May and had $6,200 in Schedule C expenses, your net SE income for Q2 is $21,800.
The 92.35% multiplier exists because the IRS lets you deduct the employer-equivalent portion of SE tax. On $21,800 net income: $21,800 x 0.9235 x 0.153 = $3,079.
Take your net SE income, subtract the deductible half of SE tax ($1,540 in this example), and apply your marginal federal bracket. If you're in the 22% bracket: ($21,800 - $1,540) x 0.22 = $4,457. Add state income tax if your state has one.
SE tax ($3,079) + income tax ($4,457) = $7,536 due for Q2. That's 34.6% of gross revenue. If you didn't set that money aside when the invoices were paid, it's coming out of your operating cash now.
The safe harbor shortcut: If you'd rather not recalculate each quarter, the IRS gives you a safe harbor. Pay 100% of last year's total tax liability divided by 4, and you'll owe zero penalty regardless of how much you actually owe this year. If your AGI exceeds $150K, the threshold is 110%. This is Form 1040-ES line 14b.
A spreadsheet that just logs income and expenses isn't a tax tracker. A real tax tracker calculates three things automatically:
| Quarter | Income Period | Due Date |
|---|---|---|
| Q1 | January - March | April 15, 2026 |
| Q2 | April - May | June 16, 2026 |
| Q3 | June - August | September 15, 2026 |
| Q4 | September - December | January 15, 2027 |
Notice Q2 only covers 2 months and Q4 covers 4. The IRS quarterly calendar doesn't split the year evenly. Your tracker needs to handle this.
The IRS charges interest on underpaid estimates at the federal short-term rate plus 3 percentage points. In 2026, that's running around 7-8%, compounded daily per quarter of underpayment.
On a $5,000 quarterly underpayment, the penalty is roughly $87-$100. Annualized across all four quarters, a freelancer who doesn't pay estimated taxes on $100K income faces $400-$800 in penalties. Not catastrophic, but completely avoidable with a spreadsheet and a separate savings account.
The simplest system that works: open a separate savings account. Every time a client payment clears, transfer 30% to the tax account. When quarterly deadlines arrive, pay from that account via IRS Direct Pay (irs.gov/directpay).
Your tax tracker spreadsheet reconciles the two: it shows what you've set aside versus what the formula says you owe. If they diverge, you catch it monthly instead of discovering a $4,000 shortfall in March.
Shopfolio's 1099 Freelancer Tax Tracker calculates SE tax, safe harbor amounts, and tax reserve status automatically. Maps to Schedule C and Form 1040-ES. $9 Lite / $29 Pro.
See the Tax TrackerHow do freelancers calculate quarterly estimated taxes?
Estimate your annual net self-employment income (gross revenue minus business expenses). Calculate self-employment tax: multiply net income by 92.35%, then by 15.3%. Add your estimated federal income tax based on your marginal bracket. Divide the total by 4 for quarterly payments. The IRS safe harbor rule says you owe no underpayment penalty if you pay at least 100% of last year's total tax liability (110% if AGI exceeds $150K) split into four equal installments.
What is the underpayment penalty for missing estimated tax payments?
The IRS charges interest on underpaid estimated taxes at the federal short-term rate plus 3 percentage points, compounded daily for each quarter you underpaid. For 2026, the underpayment rate is approximately 7-8%. On a $5,000 underpayment for one quarter, the penalty is roughly $87-$100. The penalty applies per quarter, so missing multiple payments compounds the cost.
When are quarterly estimated tax payments due in 2026?
Q1 (Jan-Mar income): April 15, 2026. Q2 (Apr-May income): June 16, 2026. Q3 (Jun-Aug income): September 15, 2026. Q4 (Sep-Dec income): January 15, 2027. Note that the quarters are not equal: Q2 covers only 2 months, Q4 covers 4 months.