Handbook / Side business

Running a side business while you keep your job

Tax-year note: Tax information on this page applies to the 2026 tax year (returns filed in 2027), from IRS pages checked in November 2026. Figures and dates are labelled with their tax year where they appear. Check current IRS pages before you rely on them.

Starting a business while keeping a job is how many self-employed people begin. The paycheck covers your living costs while you test whether customers will pay. But a side business has its own set of constraints: limited hours, an employer's rules, and tax that nobody withholds for you. This guide covers how to run one sensibly. The tax figures it mentions are for the 2026 tax year, from IRS pages checked in November 2026.

Step one: read your employment terms

Before you take a single client, read your employment contract, offer letter and employee handbook for:

• Outside work or moonlighting. Some employers require disclosure or approval.
• Conflicts of interest. Working for competitors or your employer's clients is often restricted.
• Use of company resources. Using a work laptop, software, or time for your side business is a common problem.
• Ownership of work. Some agreements claim rights to work you create, especially if related to your job.
• Confidentiality. Knowledge from your job cannot become your side business's advantage.

If a clause is unclear, ask HR in writing or get advice. A side business that costs you your job, or creates a legal dispute, is not worth it. Keep a clean line: separate equipment, separate accounts, and side work only outside working hours.

Step two: be honest about hours

The constraint in a side business is time, not ideas. Work out what you can sustain:

Example weekly budget: Weeknights: two evenings, 2 hours each. Saturday morning: 3 hours. Total: 7 hours a week, of which about 2 go to admin, messages and invoicing. Real client work: about 5 hours.

That budget shapes everything. It tells you how many clients you can take, how fast you can deliver, and what kind of business fits. Services with fixed appointment times during the working day may not fit. Work you can do asynchronously, in evenings or weekends, usually fits better.

Put the hours in your calendar and treat them like appointments. Also block time off. Burnout ends more side businesses than a lack of demand.

Step three: set it up as a business from day one

Even small, a side business is a business for tax purposes if you run it for profit with continuity and regularity. That is the test the Schedule C instructions describe, and a hobby does not qualify. Treat it accordingly:

• Open a separate bank account and route all business income and expenses through it.
• Keep a simple ledger of income and expenses.
• Issue proper invoices.
• Keep receipts.
• Check whether your city or county requires a license for your activity.

These habits cost little and make tax time simple.

Step four: handle the tax

The IRS gig work page is direct: you must file a tax return if you have net earnings from self-employment of $400 or more from gig work, even if it is a side job, part-time or temporary. You must report all income, even if you do not receive Forms 1099 from those who pay you. Net earnings from self-employment are also subject to self-employment tax, in addition to income tax.

Because no one withholds tax from side-business income, you have two ways to pay during the year:

1. Increase withholding at your job. The IRS Tax Withholding Estimator lets you estimate how much your employer should withhold, and you can download a completed Form W-4 to give your employer. It asks for payment records for self-employment or gig work if you have them.
2. Make estimated tax payments. The 2026 Form 1040-ES gives the four due dates and safe-harbor rules. It also notes that wage earners may be able to avoid estimated tax by having more withheld.

Many people with a steady job find withholding simpler: one form, and the extra tax comes out of each paycheck automatically. Others prefer estimated payments so the side business carries its own tax. Either way, set aside a share of each side-business payment until you know the real figure.

Step five: decide what success means

A side business can be a permanent second income, a test before going full-time, or a creative outlet that pays for itself. Decide which, because each implies different choices:

• Permanent side income: keep it small and efficient; prioritize repeat clients and low admin.
• Test before leaving: track the numbers that matter for the leap, such as monthly net profit, the number of reliable clients, and the hours needed to produce them.
• Pays for itself: keep expenses low and accept slower growth.

Write a stop rule as well. For example: if side work causes missed deadlines at my job for two months running, I reduce clients.

Before going full-time

If the side business is a test, write down the conditions for leaving your job before you are tempted to quit on a good month: savings, net profit over several months, health coverage plans, and the clients you would keep. The site's guide to becoming self-employed covers the transition.

A side business works when it has its own hours, its own bank account and its own tax plan, and never borrows any of them from your job.