People who wait until March or April to start figuring income taxes should think about getting out the green eyeshade and pocket calculator now. Whatever incentive people may have needed to start year-end tax planning was handed to them in August when Congress passed the 1981 Tax Act. While there is less than a month of 1981 left, that's still enough time to find a few ways to save on tax bills.
There are more things you can do to legitimately ease your tax burden than can be listed here, but tax specialists start with this rule of thumb: deductions in '81; income in '82.
Delaying the receipt of money may go against the grain of most people. But any income received next year will be taxed at a lower rate, and with the tax brackets going up, the extra money will be less likely to push you into a higher one.
So if your boss is planning to express his appreciation with an annual Christmas bonus, tell him to keep it until January. He can tell you how much it's going to be so you'll know your limits when you do credit-card Christmas shopping. By the time the bills come, you'll have your bonus and be able to pay them without incurring any interest.
Similarly, if people owe you money for a particular job, such as free-lancing , home improvement work, or a sales commission, see if they can pay you next year. Or send out your bills late. They'll be able to earn more interest on their money and you'll get the extra income at lower tax rates.
If you have quite a bit of outside income as well as wages, however, you may be one of those who make estimated income tax payments, based on the previous year and on expected withholding from your wages. But withholding levels dropped on Oct. 1, so your estimate made last January may not be enough. Check it out, and if it is not enough, prepare for an extra tax payment before April 15. If you do not, you may have to pay a penalty, too.
This year, the penalty could be a big one. Congress has gotten tougher on those who underpay. Until now, some people thought the 12 percent penalty was a cheap loan, considering today's high interest rates. But beginning next Feb. 1, the penalty will be pegged to the prime rate of a year earlier. So for 1982, the penalty is 20 percent.
Because income received this year is taxed at a higher rate than what's received next year, deductions are more important than ever. For instance, consider making the 1982 contribution to your favorite charity now and taking the deduction when it does the most good. If you don't have the money right now, many charities accept credit cards, so even if you pay the bill in 1982, you can take the deduction in 1981.
Another big deduction is for people who own real estate - like their house. This is the property tax. If you can prepay some of your 1982 property tax now, do it, take another deduction, and make your town fathers happy. They can use the cash. Likewise, if you can prepay a mortgage installment and get some additional interest charges paid in 1981, that's another deduction.
If you're thinking about buying a new car and the old clunker won't wait until auto loan rates come down, you can get some solace by buying the new one now and deducting the sales tax.
Do you have a lot of money in a money market fund? Think about using some of it to buy Treasury bills maturing after Jan. 1. The first advantage is that you get to defer the interest that would be earned between the date of transfer and 1982, when the bills mature. Also, with interest rates coming down with a longer-term bill, you'll lock in higher yields than many of the funds will probably be paying six months from now.
Perhaps you have some poorly performing stock recommended by a friend - who is no longer employed by the brokerage firm. If the stock shows little hope of recovery, sell it now. The deductible loss can be taken for 1981, offsetting any gains.
As for selling stocks with a gain, since the top rate on long-term capital gains drops to 20 percent for sales made after June 9, 1981, there is no real tax advantage for people who are in the 50 to 70 percent tax bracket to postpone sales to 1982. But sellers below the 50 percent bracket should consider delaying year-end gains until 1982 - another way to push income into next year.
And there is something else two romantic working people might consider pushing into next year: their wedding. Because the new tax law liberalized the so-called ''marriage penalty,'' a two-income couple will likely do a little bit better filing their first joint return next year. Small business aids
I soon plan to open my own business. With many businesses going bankrupt and the cost of living rising, I don't want to make a mistake. Where can I find more information about investments and new businesses? - R. V.
Interest in owning a small independent business is booming, and cottage industries are on the increase. Many individuals are once again dreaming the American dream of being one's own boss and ''doing my own thing.'' Many individuals with entrepreneurial spirits figure that with the tax overload on salaries and wages, their only hope for ''hitting it big'' is in their own business. As a result, numerous good books have emerged. Three helpful ones are ''How to Become Financially Successful by Owning Your Own Business,'' by Albert J. Lowry (New York: Simon & Schuster, $14.95); ''The No. 1 Home Business Book,'' by George and Sandra Delany (Liberty Publishing Company, $4.95); and ''Start Your Own Small Business the Right Way!'' edited by Louis Mucciolo (New York: Arco Publishing Company, New York, $8.95).