The First-Year Business Owner's Tax Guide

Why year one catches everyone off guard

When you work as an employee, taxes are invisible. Your employer withholds the right amount from every paycheck, deposits it to the IRS on your behalf, and hands you a W-2 in January. You file. Maybe you get a small refund. It feels painless.

When you start a business, that system disappears. Clients pay you gross. Nobody withholds anything. The IRS still expects its share — quarterly, in advance — but you have to calculate it, save for it, and send it yourself. First-year owners who don’t know this exist face an April bill of $8,000–20,000 with no money set aside.

This guide covers the three things you need to understand in your first year: what self-employment tax is and why it’s larger than expected, how the quarterly payment system works, and which deductions to start tracking right now.

Self-employment tax explained

As an employee, you pay 7.65% in FICA taxes (Social Security and Medicare) from your paycheck. Your employer matches that 7.65% and pays it separately. Total: 15.3%.

As a self-employed person, you pay both sides. That’s the self-employment tax — 15.3% of your net profit, on top of ordinary income tax. It applies to the first ~$176,100 of net profit; above that, the Social Security portion (12.4%) stops, but Medicare (2.9%) continues with no cap.

At $60,000 in net profit, that’s roughly $8,478 in SE tax before income tax starts. At $100,000, it’s about $14,130. Most first-year owners don’t realize SE tax exists until they owe it.

The surprise isn’t that you owe — it’s the scale. SE tax often exceeds income tax for owners in the first few years. Plan for it first.

Your business foundation

Before your business earns its second dollar, two things need to exist: a separate business bank account and a basic bookkeeping system. These are not optional — they are the foundation that makes every tax calculation possible.

Separate business bank account

Mixing business and personal money in the same account creates three problems: you can’t tell what the business actually earns, tracking deductions becomes a reconstruction project, and if you ever get audited, the IRS treats the entire account as potentially taxable.

• Open a business checking account at any bank — most business checking accounts have no monthly fee if you maintain a small minimum balance
• All client payments go into this account; all business expenses come out of it
• Pay yourself from the business account into your personal account — this is called an owner draw
• Never pay personal expenses directly from the business account

Basic bookkeeping from day one

You don’t need an accountant to do bookkeeping. You need a system. At minimum: track income and expenses in a spreadsheet or simple software (Wave is free; QuickBooks Self-Employed and FreshBooks are affordable). Categorize each transaction when it happens — not in March when you have twelve months to reconstruct.

Do you need an EIN?

An Employer Identification Number (EIN) is a federal tax ID for your business — like a Social Security number for the entity. You need one if you hire employees, run payroll, open a business bank account (some banks require it), or operate as a partnership or corporation. Sole proprietors without employees can use their SSN for tax purposes, but getting an EIN adds a layer of separation between your personal and business tax identities. It’s free and takes five minutes at irs.gov.

The quarterly tax system

The federal government expects taxes to be paid as income is earned throughout the year — not in a lump sum in April. For employees, this happens automatically through payroll withholding. For self-employed people, it happens through estimated tax payments made four times per year.

The four quarterly due dates

• Q1 (Jan–Mar): Due April 15
• Q2 (Apr–May): Due June 16
• Q3 (Jun–Aug): Due September 15
• Q4 (Sep–Dec): Due January 15 of the following year

If you miss a payment or underpay, you don’t get a penalty notice — the underpayment penalty is simply calculated when you file your return. It’s usually a few hundred dollars, not catastrophic, but it’s avoidable.

How to avoid the penalty

Two safe harbors let you pay the correct amount without calculating your exact current-year tax:

• Prior-year safe harbor: Pay 100% of what you owed last year (110% if your AGI exceeded $150k), split across four payments. If last year was your first business year, this method only works after you have a full prior year return.
• 90% of current-year tax: Estimate what you’ll owe this year and pay 90% of it across four payments. Requires updated books.

Deductions from day one

Every legitimate business expense reduces the profit that SE tax and income tax are calculated on. Tracking deductions is not optional — it’s how you pay tax on what you actually earned, not on gross revenue.

Deductions most first-year owners miss

• Home office: If you have a dedicated space used exclusively and regularly for business — even a specific corner of a room — a portion of your rent/mortgage, utilities, and internet is deductible.
• Self-employed health insurance: If you pay for your own health coverage and aren’t eligible for an employer plan through a spouse, 100% of your premiums reduce your AGI above the line.
• Business phone and internet: The business-use percentage of your phone and home internet is deductible. Most service businesses support 60–80% phone and 50–70% internet.
• Software and subscriptions: Any software, app, or subscription used for your business — scheduling, accounting, design, communication — is fully deductible.
• Professional development: Courses, certifications, books, and conferences that maintain or improve skills in your current work are deductible. Education for a new career is not.
• Startup costs: Up to $5,000 of startup expenses (legal fees, business registration, initial equipment, website setup) can be deducted in your first year.

Start retirement savings early

The best time to open a retirement account is the year your business starts earning real money. Every dollar you contribute reduces your taxable income — which reduces both income tax and SE tax.

A Solo 401(k) is generally the best option for a single-person business. In 2026, you can contribute up to $70,000 in combined employee deferral ($23,500) and employer profit-sharing contributions. The full amount is deductible.

• Solo 401(k): highest contribution limits, most flexibility, must be established by October 15 of the contribution year
• SEP-IRA: simpler to set up, can be opened up to the filing deadline (with extensions), limited to ~20% of net SE income
• Traditional IRA: not specifically business-oriented but available as a supplement; $7,000 limit in 2026

Even a $5,000–10,000 contribution in your first year saves $700–1,400 in SE tax alone, plus reduces your income tax. Start this habit early — before other expenses expand to consume what would have been contributions.