Last week I discussed preparing for a tax audit. I have one more bit of advice: Don't go into an audit with a chip on your shoulder.

As I said, IRS examiners are ordinary people trying to do their jobs. But they know that job is an unpopular one, the butt of comics and cartoons everywhere.

In this highly complex arena there is certainly room for differences of opinion. But you accomplish nothing by getting mad at the examiner or heaping on his shoulders your frustration with the system.

So be polite, be brief, be honest. Provide all needed evidence and present your side of the story. A harangue about the tax system in general and your sad story in particular can be counterproductive. The examiner is a taxpayer too, remember--and besides, he's heard all the war stories already.

Now what happens when the audit is finished? In a simple case the examiner may tell you right then that there is no change, that you owe additional tax or that you have a refund coming. Then he will ask you to sign an agreement form.

If the situation requires some lengthy calculations or perhaps further review, you will get the results by mail.

In either case, if you agree with the findings you can sign the agreement. And you can either pay any additional tax then or wait until you get a bill. Interest is charged (or paid to you, if you get a refund) from the due date of the original return.

Generally there is no penalty unless fraud is alleged. On rare occasions a penalty may be assessed if the IRS believes you have been negligent in keeping records or reporting income (as opposed to fraud, which implies intentional omissions).

If you don't agree with the findings you can ask to meet with the examiner's supervisor. If the problem isn't resolved at that meeting, you have two options.

You can appeal the findings within IRS channels by requesting an appeals conference. A member of the IRS region appeals office will discuss the case with you and your representative (or with the representative alone if you prefer).

The other option is to take your case to court. (You can also go to court later if you aren't satisfied with the result of the appeals conference). Again you have to choose one of two channels.

If you don't want to pay the tax first, you go to the U.S. Tax Court, where most tax disputes of individuals are heard. One advantage of the Tax Court is a special procedure for small cases, when the amount in dispute for any one tax year is $5,000 or less.

You pay only a small filing fee. The hearing is relatively informal, without the strict adherence to the rules of evidence required in other tribunals, so you can plead your own case if you wish.

The other avenue is a suit in a U.S. district court or the U.S. Court of Claims. Don't try either of these without a professional--you must know the rules to play this game.

To bring suit in a district court or the Court of Claims you must first pay the full amount of the tax including any interest, then file a claim for refund of the amount you believe to be excessive. You can file suit only after you receive a notice of disallowance of your claim from the IRS.

Now let's go back to the beginning. When can you expect that fateful letter from the IRS?

For most people the answer is ''Never.'' Less than 2 percent of all individual returns are ever audited; and the percentage is lower for incomes under $25,000.

Generally the IRS has three years from the due date of the return (or the filing date if you get an extension). So for a 1981 return, filed by this April 15, the audit term will expire April 15, 1985. Audit letters on 1981 returns will start going out in the fall of 1982.

(There is no statute of limitations if fraud is suspected; and the audit period is six years if you fail to report income amounting to 25 percent or more of what was reported.)

Finally, getting a refund check doesn't mean that your return has been accepted. Refunds and audits are two separate processes; the issuance of a refund check is no assurance that your return will not be selected later for an audit.