Once in a blue moon a reader writes in to my real estate column complaining that -- "Our property tax assessment is too low!"

Turns out, usually, that they're worried about the eventual sale of their property. Will buyers assume the place is worth less than they're asking for it? And should they protest and ask that the assessment be raised?

Well, of course they shouldn't. Well-informed buyers know that however well-intentioned and skilled, the assessor's figure is still just an estimate, and is seldom a reliable guide to market value. Meanwhile, a lower property tax can be a plus from the potential buyer's point of view.

But usually, the complaint is quite the opposite.

In some communities, assessment is automatically changed to the sale price when property is purchased and that's that. It's hard to argue that the place isn't worth what you just paid for it.

Elsewhere, though, there is often room for appeal, when you think you're being asked to pay more than your fair share of property taxes.

Protest strategies differ in various locations, but one first step is the same everywhere: call at the assessor's office in your city, town or village hall, and ask to see the figures on your property. Check that your lot size and the square footage of your building are correct, and that the rest of the data is accurate. If you find a significant error, you shouldn't have trouble arranging a change in your assessment.

In some states, the next step is to look over the tax records (which are open to the public) to see how your assessment compares with your neighbors', particularly with those houses and lots substantially similar to yours. If you can back up your claims of "unfair" with hard figures, you have a good chance of winning some concession.

In other states, the only data that counts is how much similar nearby property has sold for recently. You may want to consult a real estate broker or appraiser for the figures.

The assessor's office can tell you how to protest. Often it's first informally to the assessor, then to a local board, either at a regular meeting or on a specific yearly date. Appeals are available if you have the time and energy to go further in the process.

And in most areas, helpful professionals are ready to take on your problem, usually charging a percentage of the first few years' saving if they can secure one for you. Again, talking with local appraisers can help you locate such help.