Congress' preholiday real-estate tax package -- wrapped up by Capitol Hill negotiators -- could be reason for an extra New Year's toast of bubbly. Or for a long-term headache.

It all depends on how much you own, and what you do with your real estate. Here's a year-end scorecard to see how you fared.

You're probably a winner if you: Own one or two homes and have a combined mortgage indebtedness on the properties of under $1 million.

Own a home and are likely to be interested in pulling out up to $100,000, tax-deductible, via an equity loan.

Own investment or business property and would like to avail yourself of the most important tax-avoidance technique for real estate in the entire federal tax code: tax-deferred exchanging.

You could be a net loser if you:

Own a home featured on TV's "Lifestyles of the Rich and Famous."

Own or plan to buy a home with a large down payment, and expect to pull substantial equity dollars out of it in future years, after the house has appreciated in value.

Of all the new tax changes affecting real estate owners, the mortgage-interest deduction and home-equity provisions will have the widest impact. From the legislation's effective date onward, American homeowners will have a $1 million "cap" on total mortgage debt that qualifies for federal interest deductions. You'll be able to borrow up to $1 million to acquire or substantially improve your first and second residences -- a statutory limit that for the time being should raise feathers only in the toniest neighborhoods.

The legislation also created a new, simplified limit on home-equity borrowing -- loans taken out for purposes other than acquisition or substantial improvements of a home. Taxpayers will be able to write off interest payments on up to $100,000 of additional debt secured by their homes for any purpose, subject only to the $1 million overall cap for home-interest deductions.

The key change here is that the extra $100,000 home-equity borrowing need not be for the narrow purposes -- qualified educational or medical expenses -- specified in current law. It can be for whatever strikes your fancy, be it vacations, cars, furniture or charge-account consolidations. These are all items that would otherwise be "consumer interest" in 1988. Paid for with debt secured by your home equity, however, they are fully deductible again.

What Congress sought to do was to rid the tax system of the mind-bending rules imposed by the 1986 Tax Reform Act. Those rules are enshrined in IRS Form 8598 (complete with four pages of instructions), and are due to arrive mailbox shortly. You may want to read them when they arrive. Fortunately, tax year 1987 may be the first and last time you'll have to puzzle over them.

The $l million cap, plus the $100,000 home-equity limit, could be more trouble than they seem at first glance. Real-estate lobbyists here argued unsuccessfully that imposition of any ceiling on mortgage deductibility -- no matter how high -- opens the door to further limits in coming years.