It has been estimated that more than 15 million Americans are “telecommuting” to work. In other words, they do the majority of work for their main source of income from home. The reasons most often cited for this trend are convenience, overhead savings and flexibility.

As a telecommuter, you may be eligible for certain tax breaks. Here is a sampling of how you might benefit from working at home.

Home-office deductions: You can deduct expenses attributable to a home office that you use “regularly and exclusively” as either your principal place of business or a place to meet or deal with clients or customers in the regular course of business. For example, if you conduct client negotiations at home, you may qualify for deductions. The tax law allows you to deduct your direct expenses plus a proportionate percentage of indirect expenses (e.g., gas and electric bills).

There is an additional test if you are an employee of a company: You must use the home office for the convenience of the employer. It is recommended that you obtain a written statement from your employer concerning this requirement.

Travel and entertainment (T&E) deductions: If you qualify for home office deductions, you can deduct travel expenses to and from other business locations. For instance, the cost of traveling to visit business clients at outside locations is deductible. Also you may be able to deduct entertainment costs following or preceding a substantial business discussion at your home. Note: The regular rules for T&E deductions continue to apply.

If you are an employee—and you meet the “convenience of employer” test—you can generally deduct travel expenses between your home office and other business locations of your company (e.g., a branch of the main office).

Computer deductions: If your employer furnishes you with a computer and peripheral equipment (e.g., a printer), the employer can write off the cost it incurs. The value is generally treated as a tax-free “working condition” fringe benefit to you. On the other hand, if you pay for the equipment yourself, you may deduct the cost only if it is required as a condition of employment and it is used for the convenience of the employer. Spell out these requirements in your employment contract.

Telephone expense deductions: The basic rule is that you cannot deduct costs associated with your home telephone line. It is treated as a personal expense. But you may write off costs of a second line installed exclusively for business use plus long-distance business calls on either line. Comparable rules apply to cell phones.

Remember that employee business expenses are treated as “miscellaneous expenses” on your personal tax return. Those expenses are deductible only to the extent the total for 2007 exceeds 2% of your AGI. Result: Try to have your employer reimburse you for any business-related expenses to avoid this result.