People type this into search every day: self employment tax reserve calculator.
The usual answer is “put 25% or 30% aside.” That is a planning habit. It is not the IRS formula. Self-employment tax is a published rate on net earnings. Income tax sits on top and depends on the rest of the return.
This page is a labeled example. It is not a tax return, and it is not personalized tax advice.
Profit first, then a rate you type
The IRS page on self-employment tax says SE tax is Social Security and Medicare for people who work for themselves. The rate is 15.3%: 12.4% Social Security and 2.9% Medicare.
Topic 554 says you usually owe it when net earnings are $400 or more. The amount subject to the tax is generally 92.35% of net earnings. Net earnings are gross income from the trade or business minus ordinary and necessary expenses.
For 2026 the same IRS page puts the Social Security wage base at $184,500 of combined wages and net earnings. Medicare has no wage base. An extra 0.9% Medicare tax can apply above a filing-status threshold. The self-employed tax center also says SE tax is those two pieces, not income tax.
The self-employment tax reserve calculator does not file Schedule SE. It reserves cash from profit at a rate you type:
(revenue − deductible expenses) × reserve rate
A loss month reserves $0. The rate is user-supplied. Expenses are whatever you mark as deductible. The tool says both of those things in its assumptions.
Fig 1
Revenue, then profit, then a reserve
The rate applies to profit, not to the invoice total.
Subtract deductible expenses from monthly revenue. Multiply the leftover profit by the reserve rate you typed.
15.3% × 92.35% = 14.13% of net profit if you want a Schedule SE style SE-tax-only rate. The default 28% is a wider buffer. It can hold income tax and a cushion. It is not a bracket.
The IRS estimated taxes page is the next step after a reserve. Quarterly payments are a separate calendar. This tool only sizes the monthly set-aside.
Example 1: the published $9,000 month at 28%
Here are the calculator defaults:
- monthly business revenue: $9,000
- deductible business expenses: $2,400
- tax reserve rate: 28%
Profit: 9000 − 2400 = $6,600.00
Monthly tax reserve: 6600 × 0.28 = $1,848.00
Annual reserve at the same pace: 1848 × 12 = $22,176.00
Calculator result
Self-employment tax reserve
- Monthly business revenue
- $9,000.00
- Deductible business expenses
- $2,400.00
- Tax reserve rate
- 28%
$1,848.00
monthly tax reserve
- Estimated monthly profit
- $6,600.00
- Annual reserve at same pace
- $22,176.00
After the reserve, 6600 − 1848 = $4,752.00 of that month is left for pay and everything else. $1,848 is 20.5% of the $9,000 invoice total, and 28% of profit.
Fig 2 · 1/3
Where the $9,000 month goes
Defaults: $2,400 expenses, 28% reserve.
Expenses
$2,400
Tax reserve
$1,848
Left after reserve
$4,752
Expenses are $2,400 of the $9,000.
The 28% reserve is $1,848. $4,752 is left after both.
The freelance hourly rate default already has a 25% buffer inside the quote. That buffer is a pricing input. This $1,848 is cash you park after the invoice is paid.
Example 2: a $2,500 side month at 30%
- revenue: $2,500
- expenses: $400
- reserve rate: 30%
Profit: 2500 − 400 = $2,100.00
Monthly reserve: 2100 × 0.30 = $630.00
Annual reserve at the same pace: $7,560.00
Calculator result
Self-employment tax reserve
- Monthly business revenue
- $2,500.00
- Deductible business expenses
- $400.00
- Tax reserve rate
- 30%
$630.00
monthly tax reserve
- Estimated monthly profit
- $2,100.00
- Annual reserve at same pace
- $7,560.00
$630 is a smaller hole. $7,560 is still a year of side-income tax if every month looks like this. The IRS $400 net-earnings test is already cleared. $2,100 is well above it.
Example 3: an $18,000 month at 32%
- revenue: $18,000
- expenses: $4,500
- reserve rate: 32%
Profit: 18000 − 4500 = $13,500.00
Monthly reserve: 13500 × 0.32 = $4,320.00
Annual reserve at the same pace: $51,840.00
$4,320 is the set-aside, not the bill. A year at this pace is $13,500 × 12 = $162,000 of profit. That is under the 2026 Social Security wage base of $184,500 if this is the only covered earnings. The calculator still does not apply the wage base. You typed 32%, so it uses 32%.
Example 4: what if I change only the reserve rate
Keep $9,000 revenue and $2,400 expenses. Change the rate.
15.3%, the published SE-tax headline:
Reserve: $1,009.80
Annual at the same pace: $12,117.60
14.13%, which is 15.3% × 92.35%:
Reserve: $932.58
Annual at the same pace: $11,190.96
25%:
Reserve: $1,650.00
Annual: $19,800.00
28% default:
Reserve: $1,848.00
35%:
Reserve: $2,310.00
Annual: $27,720.00
15.3% on raw profit over-reserves SE tax a little, because Schedule SE first multiplies by 92.35%. 14.13% is the closer SE-tax-only stand-in. 28% and 35% are holding income tax too.
Fig 3 · 1/5
The same $6,600 profit at four rates
Revenue $9,000. Expenses $2,400.
- Monthly reserve
| Category | Monthly reserve |
|---|---|
| 14.13% | $933 |
| 15.3% | $1.0k |
| 25% | $1.6k |
| 28% | $1.8k |
| 35% | $2.3k |
14.13% reserves $932.58. 15.3% reserves $1,009.80.
25% is $1,650. 28% is $1,848. 35% is $2,310.
Example 5: what if expenses double
Keep $9,000 and 28%. Raise expenses from $2,400 to $4,800.
Profit: 9000 − 4800 = $4,200.00
Monthly reserve: 4200 × 0.28 = $1,176.00
Annual at the same pace: $14,112.00
The reserve drops 1848 − 1176 = $672.00. That is 28% of the extra $2,400 of expenses. Spending more on the business cuts the set-aside only if those costs are really deductible. The tool does not audit the expense box.
Example 6: the common mistake, reserve on revenue
Keep 28% and $9,000. Put $0 in expenses.
Profit the tool sees: $9,000.00
Monthly reserve: 9000 × 0.28 = $2,520.00
Annual at the same pace: $30,240.00
That is $2,520 − $1,848 = $672.00 too high against the default month, because the $2,400 of costs never left the base. Topic 554 says net earnings subtract ordinary and necessary expenses first. Skipping that step taxes the invoice, not the profit.
Calculator result
Self-employment tax reserve
- Monthly business revenue
- $9,000.00
- Deductible business expenses
- $0.00
- Tax reserve rate
- 28%
$2,520.00
monthly tax reserve
- Estimated monthly profit
- $9,000.00
- Annual reserve at same pace
- $30,240.00
Example 7: a loss month
- revenue: $2,000
- expenses: $2,800
- reserve rate: 28%
Profit: 2000 − 2800 = −$800.00
Monthly reserve: $0.00
Annual reserve at the same pace: $0.00
The tool will not reserve a negative number. A single red month does not erase tax on the profitable months. Average the year, or run each month and add the reserves. The $400 IRS test is annual net earnings, not one invoice.
Example 8: a slow month at the same 28%
- revenue: $4,200
- expenses: $2,100
- reserve rate: 28%
Profit: 4200 − 2100 = $2,100.00
Monthly reserve: 2100 × 0.28 = $588.00
Annual at the same pace: $7,056.00
$588 is 1848 − 588 = $1,260.00 under the default month. If three months look like this and nine look like the default, a blended year is not 12 × $1,848.
Nine default months: 9 × 1848 = $16,632.00
Three slow months: 3 × 588 = $1,764.00
Year total: $18,396.00
That is $22,176 − $18,396 = $3,780.00 under a flat default year.
Fig 4 · 1/2
Reserve if every month stays this busy
28% on profit. One line per pace.
Cumulative reserve
- Default month
- Slow month
| Point | Default month | Slow month |
|---|---|---|
| 0 | $0.00 | $0.00 |
| 3m | $5.5k | $1.8k |
| 6m | $11k | $3.5k |
| 9m | $17k | $5.3k |
| 12m | $22k | $7.1k |
The default month is $1,848. Twelve of those are $22,176.
The slow month is $588. Twelve of those are $7,056.
Example 9: the same profit inside a freelance rate
The freelance hourly or day rate calculator default needs $118,000 of revenue to take home $80,000 after a 25% buffer and $18,000 of overhead.
$118,000 ÷ 12 = $9,833.33 of monthly revenue at a flat pace.
Put $18,000 ÷ 12 = $1,500.00 in the expense box and keep 28%. The calculator prints:
Profit: $8,333.33
Monthly reserve: $2,333.33
Annual reserve at the same pace: $28,000.00
The freelance tool already grew the quote by 25% of $80,000, which is $20,000. $28,000.00 is a different buffer. Use one model for the quote and this one for the transfer to savings after the client pays.
Fig 5 · 1/2
Three months, two expense levels
Revenue stays $9,000. Rate stays 28%.
- Left after reserve
- Tax reserve
| Category | Left after reserve | Tax reserve |
|---|---|---|
| $2,400 exp | $4.8k | $1.8k |
| $4,800 exp | $3.0k | $1.2k |
Profit is $6,600 with $2,400 of expenses and $4,200 with $4,800 of expenses.
The reserve is $1,848 on the first profit and $1,176 on the second.
$4,200 − $1,176 = $3,024 left after the fatter expense month. Both bars start from the same $9,000 invoice.
The nine months next to each other
| Example | Revenue | Expenses | Profit | Rate | Monthly reserve | Annual at that pace |
|---|---|---|---|---|---|---|
| 1. Defaults | $9,000 | $2,400 | $6,600 | 28% | $1,848.00 | $22,176.00 |
| 2. Side month | $2,500 | $400 | $2,100 | 30% | $630.00 | $7,560.00 |
| 3. Busy month | $18,000 | $4,500 | $13,500 | 32% | $4,320.00 | $51,840.00 |
| 4a. 14.13% SE-only | $9,000 | $2,400 | $6,600 | 14.13% | $932.58 | $11,190.96 |
| 4b. 15.3% headline | $9,000 | $2,400 | $6,600 | 15.3% | $1,009.80 | $12,117.60 |
| 4c. 35% buffer | $9,000 | $2,400 | $6,600 | 35% | $2,310.00 | $27,720.00 |
| 5. Expenses double | $9,000 | $4,800 | $4,200 | 28% | $1,176.00 | $14,112.00 |
| 6. Revenue mistake | $9,000 | $0 | $9,000 | 28% | $2,520.00 | $30,240.00 |
| 7. Loss month | $2,000 | $2,800 | −$800 | 28% | $0.00 | $0.00 |
| 8. Slow month | $4,200 | $2,100 | $2,100 | 28% | $588.00 | $7,056.00 |
Open the self-employment tax reserve calculator with this month’s revenue, the expenses you can defend, and a rate you picked on purpose. Use 14.13% if you only want a Schedule SE style SE-tax stand-in. Use a higher rate if the box is also holding income tax.
The gross to net pay post is the employee cousin. That tool starts from a paycheck, not from profit. The freelance rate tool is the quote before any of this cash is reserved. Publication 334 is the IRS small-business guide if you need the return, not the reserve.