The biggest debate going on now over President Reagan's economic proposals is whether his across-the-board tax cut of 10 percent a year for three years is fair to everybody.

I have found a class of Americans who believe that it isn't.

I sat next to a man at dinner who was discussing Reagan's tax cuts and felt that people like himself had been ignored. He was a builder and real estate man of great affluence.

He said in principle he was for Reaganomics, particularly where it concerned the eliminating of federal government controls on business, and cracking down on environmentalists and welfare cheaters.

Where he differed with Reagan, Stockman & Company was in their tax policies.

"But you will be getting a 10 percent cut like everybody else," I told him.

"No, I won't," he said.

"Why not?"

"Because I don't pay any taxes at all."

"How come?"

"I've been able to write off all my interest, plus my depreciation and take losses on my buildings, so I haven't had to pay taxes for five years."

"That's marvelous," I said. "It seems to me that's better than getting a tax cut of a lousy 10 percent."

"Don't you see?" he said. "People like myself are really being discriminated against. We don't get anything back from the Reagan tax cut plan."

"But if you don't pay taxes, why should you get anything back?" I asked.

"Because Reagan says his tax cut plan is fair to everybody in this country. Why should we suffer just because we're smart enough to figure out legal ways of not paying any taxes?"

"I'm sure someone must have an answer to that question," I said. "Are there many people in your predicament?"

"There are hundreds of thousands in this country. We don't make a big deal of it, so that's why we're being ignored. I have a friend in the oil business who, because of depletion allowances, hasn't paid taxes for 10 years. He has four kids in college and keeps up three homes, a boat and a private airplane. The inflation is killing him, but does the government care? Hell no. Their attitude is to just take care of the taxpayers and let the one who don't pay taxes fend for themselves."

"But you people have loopholes and tax shelters and other sources of income that the average taxpayer doesn't have available to him. Maybe that's why you were left out of the Kemp-Roth plan," I suggested.

"That still doesn't make it fair. If it wasn't for people like myself, nothing would trickle down to the middle and poor class."

"How do you suggest wealthy people who don't pay taxes be put on an equal footing with those who do?"

"We should get tax credits against the day when some of us may have to pay taxes. Suppose a Marxist leftwing Congress decides to do away with our loopholes, and we wind up having to pay our share of the tax burden? Where are we going to get the money to do it?"

"You'll probably have to sell your tax-free bonds," I said.

"Exactly. The very bonds that most of us have set aside for our old age. Look, we're not the only people who don't pay any taxes. The poor don't pay taxes either, and yet Reagan says he's putting a safety net under them so they won't get hurt. Why won't he put a safety net under us as well?"

"I can't speak for the President," I said. "Maybe he feels you people should make it on your own."

I could tell he was hurting when he said, "The really rich get it in the neck every time. If it wasn't for our lawyers and accountants, we wouldn't have a friend in the world."