Write-offs for your home business

Dear FSB: I have a small Web design business. How do I write off supplies (especially computers, software and electricity) for the business knowing that I also run my home items on the same computer? What percentage can I write off?

- Bill G., Fountain Valley, Calif.

Dear Bill: At some point nearly everyone running a home-based business asks the same question - how do I mark where work ends and life begins, and what does that mean come tax time?

"There's two ways to look at it," says Grafton "Cap" Willey, past chair of the National Small Business Association and a senior partner with Tofias PC, a New England accounting and professional services firm. "There's the technically correct way, and the practical way."

The technically correct way is for you to log exactly the time spent using the computer - and whatever other equipment you use - for business and for pleasure.