You did the work, the money came in, and then your tax preparer showed you a number that made your stomach drop. A big chunk of it was not even income tax. It was something called self-employment tax, and for a lot of first-time business owners it is the single biggest surprise on the whole return.
The good news is that this tax is not a mystery once someone explains it. In this guide we will show you exactly what the 15.3 percent is, who owes it, how to estimate your own bill with real numbers, and how an S-corp election can lower it (along with the costs nobody warns you about). Let us walk through it together.
The 15.3 Percent, Explained in Plain Words
Self-employment tax is just Social Security and Medicare tax (the money that funds your future Social Security checks and Medicare health coverage). When you have a regular W-2 job, you pay half of this and your employer quietly pays the other half. You probably never noticed it.
When you work for yourself, you are both the worker and the boss. So you pay both halves. That is where the 15.3 percent comes from.
Here is the breakdown:
- 12.4 percent goes to Social Security. This part only applies up to a yearly wage cap (a ceiling that the government raises a little most years, around $168,600 in recent years). Profit above the cap does not get charged the Social Security piece.
- 2.9 percent goes to Medicare. This part has no cap. Every dollar of profit is subject to it.
Who Owes It and When It Kicks In
If you are a sole proprietor (one person running a business with no formal company), a single-member LLC (a one-owner limited liability company), or a partner in a partnership, you generally owe self-employment tax on your business profit, which is your income after expenses.
The threshold is low. If your net profit is about $400 or more for the year, you owe it. That means side hustles count too. A Chandler teacher selling coaching on weekends and a Queen Creek online seller running a Shopify shop are both on the hook once they clear that small amount.
A Gilbert landscaper example
Say you run a landscaping business in Gilbert and after all your expenses you netted $80,000 in profit. The tax does not apply to the full $80,000. It applies to about 92.35 percent of it, which we will explain in a second. That gives you roughly $73,880. Multiply by 15.3 percent and you get about $11,300 in self-employment tax, on top of any income tax you owe. That is real money, and it is why planning ahead matters so much.
How to Calculate What You Will Roughly Owe
Let us slow down and do the math step by step so you can run it on your own numbers.
- Start with your net profit. In our example, $80,000.
- Multiply by 92.35 percent. The tax law lets you shave off a small slice first, so you are taxed on $73,880 instead of the full amount. This is just how the formula works.
- Multiply that by 15.3 percent. $73,880 times 0.153 is about $11,300. That is your self-employment tax.
There is one piece of relief. You get to deduct half of your self-employment tax when you figure your income tax. On roughly $11,300, that is about $5,650 that comes off your taxable income. Be careful here: it does not cut your self-employment tax bill. It only lowers the income that your separate income tax is based on, so it saves you a smaller amount depending on your bracket.
To see your real combined rate, you stack the two taxes together. A Mesa owner might pay 15.3 percent in self-employment tax plus, say, 12 percent in federal income tax and a little Arizona state income tax. Suddenly a healthy slice of every profit dollar is spoken for. If you want to see how the income tax side works alongside this, our guide on how much to set aside for taxes walks through the full picture.
How an S-Corp Election Can Lower the Bill
Once your profit gets healthy, there is a legal move that can shrink the self-employment piece. It is called an S-corp election (a tax status your LLC can choose that changes how the IRS treats your pay).
The mechanics work like this. You put yourself on payroll and pay yourself a reasonable salary. That salary gets the full 15.3 percent Social Security and Medicare treatment, same as before. The rest of the profit comes to you as a distribution (an owner payout), and distributions do not get charged self-employment tax.
A worked comparison at $120,000 of profit
As a plain sole proprietor with $120,000 of profit, your self-employment tax is about 15.3 percent of $110,820, or roughly $16,955.
Now say you elect S-corp status and pay yourself a reasonable salary of $60,000, taking the other $60,000 as a distribution. The payroll taxes on the $60,000 salary come to about $9,180. The $60,000 distribution skips the tax entirely. Before costs, that is roughly $7,700 in savings.
The Hidden Costs of an S-Corp Nobody Mentions
That $7,700 looks great until you count what it costs to run an S-corp properly:
- Payroll service fees. You now have to run real payroll, usually a few hundred to around a thousand dollars a year.
- A separate business tax return. An S-corp files its own return (Form 1120-S), which typically adds $1,000 to $1,500 in preparer fees.
- Stricter bookkeeping. Clean records stop being optional. You need tidy books all year.
Because of those costs, the S-corp math usually does not start working until your profit is somewhere around $60,000 to $80,000 or more. Below that, the fees can eat the savings. And if your books are sloppy, a wrong profit number can wipe out the benefit and create real compliance risk. If your QuickBooks is a mess, start with our guide to cleaning up a messy QuickBooks Online before you make any election.
How to Plan for It All Year Instead of Panicking in April
The reason self-employment tax feels brutal is that no employer is withholding it for you. You have to set it aside yourself. The fix is simple in theory: pay quarterly estimated payments (four tax payments spread across the year instead of one big April bill) and put money away from every deposit.
All of this only works if your profit number is accurate. A guessed number gives you a guessed tax bill. This is where doing your books right every month pays off, and it is exactly what we do at GGS. We keep your profit accurate month after month so your estimates are real, not wishful, and we coordinate the actual tax filing through our licensed CPA partners so nothing falls through the cracks. You can see how the ongoing help works on our services page, and grab the free tools on our resources page to get started today.
Every business is different, so please confirm your specific situation with a tax professional before you make an election or lock in a set-aside percentage. If you want a second set of eyes on your numbers, a quick call with our Mesa team is free.
The short version
- Self-employment tax is 15.3 percent (12.4 percent Social Security plus 2.9 percent Medicare), the same taxes a job splits with an employer, except you pay both halves.
- It applies to about 92.35 percent of your business profit and is separate from income tax, so you can owe it even in a low income tax year.
- You generally owe it once your net profit hits about $400, which means side hustles count too.
- An S-corp election can lower the bill by splitting pay into a reasonable salary plus distributions, but payroll fees, a separate return, and clean books usually make it worthwhile only around $60,000 to $80,000 of profit or more.
- Set aside 25 to 30 percent of every deposit and pay quarterly so April is a non-event, and keep your books accurate so the estimate is real.
Questions owners ask us
Do I owe self-employment tax if my business lost money or barely broke even?
Is self-employment tax on top of income tax, or instead of it?
Will forming an LLC lower my self-employment tax?
When are quarterly estimated payments due?
Stop letting the 15.3 percent catch you off guard
GGS keeps your profit accurate every month and coordinates your filing through licensed CPA partners, so your tax set-aside is real and April is boring. Book a free intro call.