Count on spending some extra time with your income tax advisor yet this month. Because of law changes, year-end income tax planning may be more valuable than usual.

The planning strategy hasn't changed much. It still makes sense to have enough income to use all your "free" deductions. Those include a personal exemption of $2,650 for you, your spouse and each dependent. There's also the standard deduction of $6,900 on a joint return or $4,150 for a single person.

Also, add in 40% of your health insurance premium and half of your self-employment tax.

All those could add up to more than $20,000. You want to be sure to have net income of at least that much. Otherwise, those deductions are lost forever.

Another general rule is to push toward the top of the 15% tax bracket if you're expecting higher income in the future. The first $41,200 of taxable income is taxed at only 15% on a joint return this year. For a single taxpayer, the 15% rate tops out at $24,650 of taxable income.

In other words, if you're holding on to grain, you may be better off to keep selling before year end until your taxable income hits the top of the 15% tax bracket.

Here are some tax changes that could affect you:

* Income averaging will make a comeback for three years -- 1998-2000. If you don't hit the top of the 15% tax bracket this year but go over it during the next three, you will have a chance to push some money back to your 1997 (and '95 and '96) tax returns if those were lower-taxable-income years. That will keep the money taxed at 15% rather than at 28% or more.

That takes some of the pressure off to push '97 taxable income to the top of the 15% bracket. But most tax advisors will still suggest that you level income with good tax planning rather than depend on income averaging.

* If you're a cash-basis taxpayer, go ahead and use deferred or installment payment arrangements for sale of commodities you produce. Lawmakers told IRS to back off on trying to call those alternative minimum tax (AMT) items. In fact, that law is retroactive to 1987.

* Capital gains tax rates are now 20% for taxpayers in the 28% tax bracket and 10% if you are in the 15% tax bracket. This is retroactive to sales on May 7, 1997, or after.

Typical assets that may qualify include land, buildings and other real estate, machinery, livestock, and investments such as stocks and mutual funds.

The lawmakers added confusion to this change, too.

For sales of assets from May 7 through July 28, 1997, the new tax rates apply if the asset was owned for more than 12 months. However, for sales of some assets on or after July 29, you must have owned the asset for more than 18 months for the new rates to apply.

Therefore, if you sold certain capital assets after July 29 that you hadn't owned for more than 18 months, you will not get the lower tax rate on that gain.

Before year end, have your tax advisor estimate the amount of your gain for the year and at what rate it will be taxed. He will need to know the date you bought, the date you sold, the purchase price, depreciation taken and the selling price.

If you are thinking about selling any capital assets between now and year end, check with your tax advisor first. Or, at least be sure you have owned it long enough to qualify for the new, lower rate.

Two other changes could affect your year-end tax planning:

* The self-employed health insurance deduction is 40% of your cost this year, up from 30%. The new tax law will continue to increase it to 100% by 2007.

* The expensing deduction for this year is $18,000 of machinery and equipment purchases, up from $17,500.