Nobody starts a business to do bookkeeping. You start it because you are good at something — cutting hair, fixing pipes, shooting weddings, baking bread — and you would rather do it for yourself. Then the business turns out to come with a second job that nobody mentioned, and most of the lessons in it are learned the expensive way.
Here are ten of them, learned cheaper. Each one links to the guide that covers it properly.
1. Nobody withholds your taxes
An employer quietly takes income tax out of every paycheck and pays half your Social Security and Medicare. When you work for yourself, nobody does either. You owe self-employment tax of 15.3% on 92.35% of your net profit, and income tax on top of that.
The money arrives whole, which makes it feel like yours. A common rule of thumb is to set aside 25–30% of profit the moment it lands. This guide works out your own percentage.
2. Taxes are due four times a year
Self-employed people pay estimated tax in four installments, not once in April. For 2026 they fall on April 15, June 15, September 15 and January 15, 2027 — and they are not evenly spaced, which catches people every summer.
The rule almost nobody mentions is the safe harbor: pay at least 100% of last year’s total tax across the four installments, on time, or 110% if last year’s adjusted gross income was over $150,000, and the underpayment penalty generally cannot apply however well this year goes. It does not shrink the bill; it only stops the penalty. The details are in quarterly estimated taxes.
3. Your bank balance is not your money
On any given day, the balance in a small-business account is a mix of the IRS’s share, next month’s rent, supplies already ordered and, somewhere underneath, your actual pay. The single most useful habit is to divide it on the way in: move the tax share to a separate savings account every time you are paid, so the balance you see is closer to the balance you have.
A separate business account makes this easier, even where the law does not require one.
4. Revenue is not income
A $5,000 month that cost $2,000 in materials, software, fuel and fees is a $3,000 month. Tax is charged on the profit, and the profit is what is actually yours. It sounds obvious, and yet most new owners can quote their sales to the dollar and only guess at their costs.
The fix is unglamorous: record every business expense, every time, in a tax category. An expense you forget is tax you pay that you did not owe. Here is what counts, and what people wrongly assume does.
5. Clients pay late, and some never do
“Net 30” becomes 45 days, then 60. A few clients simply never pay. That is not a reflection on your work; it is a feature of selling to other people on credit.
Three habits help more than any amount of firmness later: a due date that names a date, not “net 30”; a deposit before you start on larger jobs; and reminder dates decided in advance, before you are annoyed. And know this before it happens: on the cash method you generally cannot deduct an invoice that was never paid, because you never counted it as income. Our guides on getting paid faster and when a client won’t pay cover the rest.
6. An LLC does not lower your taxes
Forming an LLC is often sold as a tax move. For a single-member LLC it isn’t one. The IRS treats it as a disregarded entity: the income lands on Schedule C of your personal return, and you pay self-employment tax exactly as a sole proprietor would.
An LLC can separate business liabilities from your personal assets, which is a real reason to form one. Electing S-corp status later can change the tax picture, but that has costs and rules of its own. Start with LLC or sole proprietor, then the S-corp question.
7. The forms do not decide what you owe
A client who pays you $2,000 or more in 2026 should send a 1099-NEC. A card processor sends a 1099-K for every dollar it processes; a payment app or marketplace sends one once you pass $20,000 and 200 transactions. Below those lines, you may get no form at all.
None of that changes what you owe. All business income is taxable whether or not anyone reports it. The forms are the IRS’s cross-check, not your income figure, so your own records need to be the complete list. More in who gets a 1099-NEC and the 1099-K.
8. Records are a habit, not a project
The IRS expects you to keep records that support your income and deductions, generally for at least three years after you file, and longer in some situations. Receipts, invoices, mileage logs, bank statements.
Mileage is the classic loss. In 2026 the standard rate is 72.5 cents a mile through June and 76 cents from July 1, so a forgotten 2,000 miles is well over $1,400 of deductions gone. A log kept as you drive survives an audit; a log reconstructed in April from memory often doesn’t. The whole thing works as ten minutes a week and fails as a weekend in April.
9. You are your own benefits department
No employer 401(k) match, no group health plan, no paid time off. All of it is now your job to fund, and the tax code gives you tools for it.
- Retirement: a SEP-IRA or Solo 401(k) can shelter up to $72,000 for 2026, and a Solo 401(k) starts with a flat $24,500 employee deferral, which makes it the stronger choice at modest incomes. See retirement without a 401(k).
- Health insurance: premiums are often deductible for the self-employed, with conditions worth knowing. See the health insurance guide.
- Time off: nobody pays you for a week away, so price it in. If you want four weeks off, your rate has to cover 48 working weeks, not 52.
10. Irregular income needs a different budget
Every budgeting method built for employees starts with a monthly income. Yours does not exist. A self-employed year is peaks and gaps that happen to average out to something, and a budget built on the average breaks the first month you fall below it.
What works instead is percentages per payment: every time money comes in, the same shares go to tax, fixed costs, savings and spending, whatever the size of the payment. A thin month gets a thin version of the same plan, not a crisis. The method is in budgeting on irregular income, and the number that tells you when you are actually safe is in your FU number.
The thing underneath all ten
Read the list again and most of it is the same lesson: know where your money stands while it is happening, not after. Tax set aside as it arrives. Expenses recorded when they occur. Invoices tracked from the day they go out. That is the whole job of the second job, and it is smaller than it looks once it is a habit.
It is also exactly what we built BrassWell to do for a business of one — and if you would rather do it with a spreadsheet, every guide linked above works just as well without us.
Questions, answered
How much should a small business owner set aside for taxes?
A common rule of thumb for the self-employed is 25 to 30 percent of profit. Self-employment tax alone is 15.3 percent on 92.35 percent of net profit, and income tax comes on top, so the right figure depends on your bracket and state.
Does forming an LLC save taxes?
Not by itself. A single-member LLC is a disregarded entity for federal income tax, so its income goes on Schedule C and is subject to self-employment tax exactly as a sole proprietorship’s would be. An LLC can provide liability protection, and an S-corp election can change the tax picture, with costs and rules of its own.
Do I have to pay tax if I didn’t get a 1099?
Yes. All business income is taxable whether or not a client or platform reports it. For payments made in 2026, clients generally issue a 1099-NEC at $2,000 or more, card processors issue a 1099-K for any amount, and payment apps above $20,000 and 200 transactions, but those thresholds only decide who files a form.
How long should a small business keep records?
The IRS says to keep records that support your income and deductions generally for at least three years after filing, and longer in specific situations such as unreported income or bad-debt deductions.
When are quarterly estimated taxes due in 2026?
April 15, June 15 and September 15, 2026, and January 15, 2027. If a date falls on a weekend or legal holiday, the payment is due the next business day.
Sources
- Self-employment tax (Social Security and Medicare taxes) — IRS. The 15.3% rate on 92.35% of net earnings.
- Estimated taxes — IRS. The four payment dates and the prior-year safe harbor, including the 110% rule above $150,000 of AGI.
- Single member limited liability companies — IRS. A single-member LLC is disregarded for income tax and its owner pays self-employment tax like a sole proprietor.
- Instructions for Forms 1099-MISC and 1099-NEC — IRS. The $2,000 reporting threshold for payments made after 2025.
- Understanding your Form 1099-K — IRS. No threshold for direct card payments; $20,000 and 200 transactions for payment apps and marketplaces.
- Standard mileage rates — IRS. 72.5 cents a mile for January through June 2026 and 76 cents from July 1.
- How long should I keep records? — IRS. The general three-year period and the longer periods for specific situations.
- One-participant 401(k) plans — IRS. The 2026 contribution limits for a Solo 401(k).
