THE IDEAL holiday office party starts before lunch, with an invitation issued by the boss. The exact wording of this invitation should be: "Why don't we take the rest of the day off?"

This is the simplest and most pleasant invitation a person in authority can issue. It does not require engaging a caterer, and it does not leave the office littered with plastic cups and personnel problems. It costs nothing and delights everyone.

Nevertheless, many people persist in the notion that office parties spread good will among co-workers. Annual experiences to the contrary never seem to dislodge this often-fatal error. Miss Manners' mean-spirited approach to professional merrymaking is actually part of an increasing hostility to the entire concept of business entertaining. From the formal diplomatic dinner to the salesperson's after-hours drink with a client, she finds it an intrusion on the worker's private life and an insult to the concept of good business. It is Miss Manners' belief that most people make their professional decisions on the basis of their best judgment, unclouded by an ecstasy of gratitude brought on by the offer of a free drink.

She also feels that disguising the business relationship as friendship produces more dangers than rewards. A person who behaves disgracefully at a party ought to lose his friends, perhaps, but not his livelihood.

In the case of an inter-office Christmas party, blurring the class lines is always a mistake. The fraudulent attempt to pass off people of different ranks and degrees of power as a bunch of jolly equals can only lead to trouble. r

Take for instance, the matter of "There's something I've always wanted to tell you." Such things, whether they involve how you feel about the short-comings of a superior, or how you feel about the personal attractions of an inferior, are always better left unsaid. That is why you didn't say them all year, isn't it? Remember?

How much nicer was the old tradition of emphasizing the distinctions of rank, with false cheer instead of frank exchange. By this system, the worker says a few words about the privilege of working there, and the boss distributes prose along with a-little-something-extra-in-the-check.

If partying is required, a paternalistic, or maternalistic, version is best, with the employer paying for the treat and the employes responding by being on their best behavior. Perhaps they can be asked to bring their immediate families to the office, and the children may be allowed to examine the premises, while the adult relatives are told how valuable is the contribution of their particular wage earner.

Perhaps this is too wholesome and unsatisfying a way for some people to celebrate the holiday with their co-workers. Well, remember that unexpected day off Miss Manners suggested as the ideal celebration? She never said you had to go directly home and spend it trimming the tree. MISS MANNERS RESPONDS

Q. Recently, I had an out-of-town guest visiting me. While she was here, we had good times meeting new people and in general having fun. Would it be appropriate for me to send her a thank-you note for the happiness she brought to me while she was here?

A. Why does Miss Manners have the feeling you think it would have been appropriate if your houseguest had written you a thank-you note some time ago, but that she didn't? If your plan is for the purpose of pointing this out to her, Miss Manners may surprise you by approving. People often mistakenly say that good manners exist only to make others feel comfortable; this is a classic example of the legitimate use of good manners to make another person feel uncomfortable.

On the unlikely chance that you already received the proper letter from her and merely want to reply that you also enjoyed the visit, Miss Manners will simply applaud your good nature and say, "Why, of course."

Q. What is the proper way to enter an elevator, please? By the time all inside have come out, the door is closing on those trying to enter. Why can't those inside come out on one side, so those going in can enter more easily. I ride elevators all day long for a delivery service, and some folks just won't give you room to get into it or hold the door. You should ride some with me -- it would make you a drinking person.

A: Thank you, but Miss Manners does not mix drinking with elevator travel because, for the reasons you describe, she considers it dangerous. But while acknowledging your problem, she sees only additional problems in your solution, what with all the people inside pushing one another to get ready for their one-sided landings. The key courtesy here is the door-holding. If the person nearest the button panel keeps the doors open long enough for the exiting, followed by the entering, more people would travel on the same side of the doors as their limbs.