Yearend tax strategy presents a greater challenge in 1985 than in many a year, given the opportunities -- and uncertainties -- created by deliberations on tax reform. How can the taxpayer best take advantage of this situation?

Some advisers recommend that taxpayers proceed on the basis of existing law with an awareness that major changes may be on the horizon. Others counsel structuring moves on the basis of the provisions Congress seems most likely to approve but with maximum flexibility in case they don't materialize. And, of course, there is always the standard caveat of judging investments on their economic merit rather than the tax benefits derived.

A number of changes go into effect anyway for the first time in tax year 1985, such as full indexing, less stringent record-keeping for business expenses, appraisals for charitable contributions over $5,000, etc. As a general rule, taxpayers should strive to defer income and accelerate deductions to take advantage of lower rates in 1986. This is true unless the individual is subject to the alternative minimum tax, in which case the reverse strategy is preferable.

The following suggestions were offered by financial planner Marvin R. Burt, president of Burt Associates Inc. in Bethesda; Judith Mero, a tax lawyer with Shulman Rogers Gandel Tobin & Ecker; and Anne L. Stone, a certified public accountant with Peat Marwick Mitchell & Co. They worked with 1985-86 changes and provisions already approved this fall by the House Ways and Means Committee or widely assumed to be in the works.

There seems to be widespread agreement that personal tax rates will go down in 1986 -- the maximum tax is expected to be 35 to 37 percent instead of 50 percent -- and that deductions will be cut back. But it cannot be emphasized too strongly that the figures given below are far from being chiseled in stone. They are the latest available and are given so that taxpayers can make tentative calculations. It is also important to remember that any of the actions discussed below should only be taken in the context of the taxpayer's complete return.

A number of opportunities involve real estate. Anyone with an inclination to move to the suburbs, where property values and taxes are generally lower, would benefit if the deduction for property, real estate, state and local income taxes is capped. One proposal would limit the deduction for real estate and state income taxes to $1,000 a year, or the amount that exceeds 5 percent of adjusted gross income.

If you plan to purchase a residence with a rental unit or an investment property, do so before the end of 1985 to take advantage of the current 19-year depreciation schedule before it is lengthened, perhaps to a proposed 30 years. It also would be smart to retain the option of prepayment without penalty so that the taxpayer can restructure the financing if necessary. This would enable a person to avoid exceeding the proposed limit on deductions for interest payments on items such as a second home, boat, cars or credit cards.

If the total interest payments for these exceed investment income by $5,000, the excess would not be deductible; thus the owner might consider refinancing the primary residence and paying off the other loans with the proceeds. There will be no limit on the deduction for mortgage interest on a principal home. Refinancing in 1985 also makes "points" paid to close a loan more valuable as a deduction.

Real estate tax shelters are considered attractive at the moment because the write-offs are expected to be grandfathered, or preserved for as long as the property is owned. Without such a provision, the value of such investments could plunge. In addition to the accelerated depreciation, by acting before yearend, you can still benefit from the 25 percent credit for certified historic rehabilitation, a category that would be cut back to 20 percent, if the Ways and Means version is accepted. Energy saving measures such as storm windows and solar heating should be put in place before yearend, because the residential energy tax credits are due to expire.

The sales tax deduction on any big-ticket item such as a car or fur is worth more in 1985, so there is an advantage in buying now. Similarly, the self-employed person or the small-business owner should not postpone a planned purchase of a computer or other equipment, because Congress is expected to knock out the 10 percent investment tax credit; a $5,000 limited expensing deduction may vanish for larger corporations. Also, take that business cruise before yearend. If you can't leave before New Year's, buy the tickets before then to benefit.

If your employer offers a tax deferred 401(k) plan, borrow if necessary to fund it to the maximum in 1985 because Ways and Means would cut back employe contributions from the current maximum of $30,000 (or 25 percent of income, whichever is smaller) to $7,000. The employer could supplement the contribution up to a total of $25,000.

Although the 401(k) offers less freedom of investment, dollar for dollar it is usually more advantageous for an employe to put money in a 401(k) because most employers match the contributions.

With a halt to 10-year forward averaging projected, a person who has the opportunity to take a lump-sum distribution from a pension program, and who does not wish to roll it over into an IRA, should do so before the end of the year. The same is probably true for a windfall, but do the numbers with income averaging to be sure. For example, if a person with an income starting at $10,000 in 1982 and growing to $25,000 in 1986 hits the jackpot for $100,000 in 1985, he or she would pay $27,520 in taxes by income averaging compared with $34,790 by deferring the income to 1986.

Try to pre-pay real estate and state income taxes, the January home mortgage and charitable contributions for 1986 to take full advantage of higher deductions this year. Defer income by having your employer put off the bonus if possible until after New Year's or buy a large discount short-term Treasury certificate on which the interest does not accumulate, but is paid at maturity in 1986.

Capital gains may be taxed at a lower rate next year. In any case, it makes sense to sell investments that show a loss this year and wait until next year to sell those showing a gain. However, if you must pay an alternative minimum tax, reverse the process. In making gifts to charity, give the stock itself if it has appreciated. If you sell it first and donate the money, you will have to pay taxes on the capital gains prior to making the gift. The reverse is true for stock that has depreciated; sell it first, take the loss and donate the money, except when subject to alternative minimum tax.