Should I register a home-based business?

Q: Hello. I'd like to create an at home business for the after-hours from my normal job. A simple computer support service, which I go to the customers home to perform a large variety of tasks. Two questions which I can't find an answer to:

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1. Do I need to "declare" myself a business with the state if I'm working from my home, or do I just start doing it?

2. What about business related expenses? Can I claim those for such a business? — Eric, Milwaukee, Wisc.

A: You don't need to file papers with the state, though if you hire others and need to withhold payroll taxes, you should get a tax ID number for the IRS. Otherwise, your Social Security number is all you need.

The only thing the IRS cares about is that you declare your full earnings and that you deduct only legitimate business expenses. The simplest way to do this is to file a Schedule C with your personal income tax return. Here are the interactions,including guidelines on what you can write off as expenses.)

And, while I've got you, is there any way to rig my son's computer so he can only play an hour of PC games a day?