By now you should have received most, if not all, of the various income tax statements for 1981 -- W-2s, 1099s for interest and dividends, etc. These information statements are required to be distributed not later than Jan. 31 each year.

The time has come to think seriously about getting started on your 1981 tax return. But if you're one of my half dozen or so faithful readers, hang on for a little while yet.

The annual Washington Post Tax Guide is scheduled for publication Monday, Feb. 22. Meanwhile you can be sorting out the tax-related documents you've been accumulating all year.

Of course there are other sources of tax advice; but we like to think our tax guide is one of the most useful. We try to avoid esoteric situations and to provide the basic information most people will need to prepare their returns, together with tax tips to keep you from overlooking important items.

And here's the first tip -- an easy way to reduce the amount of work involved.

Prepare your tax return in pencil. When you have finished both federal and state returns and are satisfied they are correct, place the mailing label from your IRS or state booklet at the top of each return -- but don't sign them.

Next go to a commercial copy store or your library or post office and have photocopies made of the penciled originals. (If your state requires copies of any federal schedules, have an extra copy made.)

Now sign each photocopy, attach all W-2s and any payment due and mail by the due date. The IRS and all three local jurisdictions will accept a photocopy of the entire return, provided only that the signatures are original on the copy you send in.

This method -- used by many commercial preparers -- makes it easy to correct entries as you work. It also eliminates the chore of transferring figures from your work copy, as well as the possibility of transcription errors.

The Investment Company Institute has published a booklet with a great deal of useful information on the new IRA rules.

The last few pages of the booklet deal with the advantages of investing your IRA money in a mutual fund. This should come as no great shock, since the Institute is the trade association for mutual fund sponsors.

But the first 18 pages give excellent coverage of the rather complex regulations, free of any sales pitch. The booklet is written in easily understandable question-and-answer format.

If you would like a free copy, send your name and address to the Investment Company Institute (IRA Booklet), 1775 K St. NW, Washington, D.C. 20006.

Q: We are over 65 and have lived in our home for more than 30 years. We have an extra lot behind the home, originally used for the septic system. (We now have sewers.) If we sold the home and extra lot, I feel we would not have to pay taxes on it. But what if we sold the lot separately?

A: I suspect you already have an idea of the answer and are just hoping you're wrong.

Unfortunately, sale of the extra lot separately from the house would not qualify for the over-55 exclusion of $125,000 of capital gain.

The reason is basic to the concept of the exclusion: To qualify, the property sold must have been your principal residence.

But the first part of your premise is correct. Capital gain on sale of both lots as a package would qualify. And this opens the door to a possible solution.

I assume you asked the question because you would like to continue to live in your home while generating some cash from sale of the lot. Perhaps you can find a buyer for both lots (and the house) who will agree to a lifetime lease of the house for your and your wife.

Such an arrangement would permit you to exclude the gain on the entire sale (up to the $125,000 ceiling) and still continue to occupy your home.

But be careful; there can be pitfalls. If you think you would like to go this route, be sure to have an attorney qualified in real estate transactions draw up the necessary agreement. This is definitely not a do-it-yourself project.