While tax sites are plentiful, it's important to keep in mind that the information you find on them is only as reliable as the sources it comes from. Make sure you know as much as possible about a site's owners, their credentials, and how long they've been providing tax information before you do something drastic like change your accounting system on their advice. Steer clear of web sites sponsored by tax protest groups because they often advocate tax positions that are overly aggressive and, in some cases, frivolous, says Dennis Schmidt, a University of Northern Iowa accounting professor who offers a directory of tax and accounting sites.

Schmidt warns that before you make any decision or take any action based on tax information you discover on the internet, you should always consult a qualified, professional advisor who understands your particular business well. Many web sites themselves point out that the information they provide is by no means a substitute for professional tax services and counseling.