You may be able to enjoy a happier, more prosperous New Year, as far as your personal finances are concerned, if you start your 1981 tax planning early.

Most of us wait until a few weeks before we prepare our tax returns to start dredging up records, receipts, income totals and the like. But by then it's too late to plan, too late to squeeze out potential deductions, credits, exemptions and income exclusions.

To get an early start on the 1981 tax year, read some books on tax planning and preparation or, better yet, see a professional tax planner or preparer.

Here are some tax areas to explore when you do your 1981 planning:

Look into increasing your savings or stock investments. This year, you will be able to exclude up to $200 in dividends and savings interest from your adjusted gross income if you're single and up to $400 if you're married. Last year the limits were $100 and $200 and savings interest was not included.

To get the full exclusion as a married couple, you could have $3,000-plus in a 30-month savings certificate paying 12.9 percent a year. Or you could have close to $6,000 worth of stocks paying 7 percent in dividends.

You can now get a bigger tax break for the use of your car in your work or for the use of your car for medical and volunteer purposes.

The new amount is 20 cents a mile (up from 18 1/2 cents) for a work-related use of your car and 9 cents (up from 8) for medical trips or volunteer work.

Be sure to check your state's tax breaks for use of your car. Maryland, for example, allows 20 cents a mile for medicalyy related volunteer work (Red Cross, taking elderly to doctors' offices and so forth).

To remind yourself of "tax trips" attach a small notebook and pencil to you car's sun visor with a thick rubber band. Note the date, purpose of the trip and the mileage (plus any additional expenses such as parking and tolls -- which are also deductible).

The rules have been eased on making installment sales to reduce the tax impact on the profit you make from selling a large hunk of property such as your own home or a rental home.

It's now a lot easier to take a down payment and a note from the seller to pay off over five or 10 years. The tax is spread out.

If there are any big changes in your life coming this year, start now to prepare for them from a tax point of view. This includes such things as divorce, selling your home, retirement, or starting a small business. Special tax consequences and opprotunities are often tied to major changes.

Start keeping organized tax records for the upcoming year. Get yourself a big calendar that allows room for notes on tax-related information. When you take a trip that may be tax deductible, note it down -- names, numbers, purpose of the trip.

If you do any business travel or entertaining, keep a "tax diary." Note the names of the clients or business associates involved, what you talked about, the reason for the meeting, lunch or whatever. Good records can be a godsend when you prepare your 1981 tax return next year. And good records can help insulate you from tax audit problems.

Q. Our daughter started college as a freshman last fall. Will she need special fire and theft insurance?

Probably not. Check with your home center renter or owner insurance company. Most students are covered under their home policies for up to 10 percent of the total coverage.

Q. For several years I have had my Social Security checks sent directly to my bank. It's called direct banking and it's a lot safer than having the checks delivered at my door. But now the banks says I have to maintain a minimum balance of $250 and I can't always do that. What should I do?

A. Change banks. These days banks and savings and loans are in hot competition to get new depositors. Look up the banks and savings and loans in your area (in the Yellow Pages) and ask if you can have your checks sent in directly from Social Security with no minimum balance requirement. I'll bet you get several offers.