Something special happened when the widower and the divorcee, each 60 years of age, struck up a conversation while they waited in a supermarket checkout line.

Before long, they were getting together regularly for dinners, movies and trips to the local museum.They had many shared interests. Their children were grown and well established with families of their own.

Neither of them was rich, but both owned homes that had appreciated greatly in value since they had bought them many years before.

So after the joyous day of their wedding, they were able to sell those houses, buy a comfortable condominium and put the rest of the proceeds in income-producing investments.

What possibly could be wrong with a happy tale like this? Well, not much maybe, but it would have been even better if the sequence of events had been altered just a bit.

The couple needlessly forfeited about $35,000 that could have paid for, say, a long honeymoon cruise.

If they had checked with a good financial adviser, they would have sold their houses first and gotten married afterward.

That way, say experts on the subject, each could have claimed a tax break sheltering $125,000 of the profits from the sale of their houses. Once they were married, they could claim that exemption only once.

The $125,000 exemption was written into the tax laws with an intent that is readily apparent - to make it more practicable for people 55 years of age or older to help finance their later years with proceeds from the sale of a home.

But the rules had to be framed so that people weren't encouraged to go into the property-flipping business on their 55th birthdays, cashing in on the tax break over and over again.

Thus was it decreed that the exclusion could be taken only once in an individual's, or a couple's, lifetime.

"Both spouses are ineligible for the exclusion if either of them previously claimed it," points out the accounting firm of KMPG Peat Marwick.

"Only one exclusion is allowed per couple. Therefore, even if the exclusion was not claimed previously, a married couple cannot claim exclusions for two homes.