The most important news of 1987 on the federal income tax front was that the new tax act went into effect, bringing lower tax rates for almost every American and lower tax bills for many. The second most important piece of income tax-related news is that Softview Inc., the developer of MacInTax, has come up with a new version of that wonderful Macintosh program that will run on IBM PCs and clones.

Loyal readers may recall that MacInTax is the world's greatest personal computer income tax-preparation software. It not only runs rings around all competing tax-form programs, it also makes filling out your federal income tax forms so fast and easy that the job almost becomes fun.

The program fills out Form 1040 and dozens of other associated forms and schedules. It performs every calculation instantly, automatically transfers figures on one form or worksheet to the appropriate line on another, keeps notes to substantiate every number on your return, and pops up the relevant section of the IRS instruction manual if you get stuck.

As if that weren't enough, MacInTax then can print each of the completed forms. You put a blank sheet of paper into your printer, and out comes a completely filled-in Form 1040, Schedule G, or whatever. The printouts are so good that the IRS accepts them in place of its own. About the only thing MaxInTax can't do is fold the printed return and stick it in an envelope.

As the name implies, MacInTax was written for the Apple Macintosh, a fact that prompted me to write last tax season that the MacInTax program alone was justification to go out and buy a Mac. But now Softview has just about completed an MS-DOS or PS/2-compatible version -- but with the same name.

I have seen a prototype of the MS-DOS MacInTax, and at this preliminary stage it looks good. Softview (Camarillo, Calif., 805-388-2626) says the program will be available in January for about $100. If you've been thinking about buying a tax preparation program, it probably will be worth your while to wait and see the new MacInTax.

MacInTax, of course, was written to perform the task of filling out federal income tax forms. But when the software became a success, the programmers at Softview began to realize that they had written more than just a tax-form program. It was a generic form-filling-out program. It worked beautifully for Form 1040, but it presumably was adaptable to any form.

So the Softview folks are working on a new, broader piece of software that sounds terrific, at least in concept. This program would permit you to replicate on your computer any form -- your expense account form, a supplier's order form, an insurance claim form or any of the other forms whose lines and columns were designed so that you can't possibly use a computer or a typewriter to fill them out. With the form on the computer screen, you could use a keyboard or mouse to jump from line to line and fill in the blocks, then print the completed form on blank paper.

To date, this program is nothing more than vaporware; it exists only in the minds of the programmers. But if Softview (or anyone else) can bring the idea to fruition in a way that is as easy to use as MacInTax, it could create a whole new category of software.

It makes you wonder why all the programmers wasting their time on recipe programs or pop-up notepads don't devote their energies to something this useful.

Another new entry in the useful ideas category is a fairly neat program called NVelope, from Paul Mace Software (Ashland, Ore.). This $49 program, which is supposed to be available in December, was designed to do two simple things -- or, more precisely, two things that ought to be simple on a personal computer but have not been.

First, it grabs the inside address of a business letter you're writing and prints it automatically on an envelope. That means you don't have to reformat your word-processing program and retype the address. I know of only one word-processing program that can do this chore -- PFS: Write, from Software Publishing. NVelope, in contrast, is designed to pop up on top of any word-processing program, find the address in your letter, and print an envelope.

NVelope also includes a specialized data-base program that can look up the zip code for many U.S. addresses. When you use NVelope to print your envelope, it will in many cases automatically throw in the zip code.

It's another nice example of somebody who found a way to make your personal computer handle a mindless, but necessary, job -- which was the whole purpose of computers in the first place.