A GASOLINE TAX -- a serious and substantial one -- is on the horizon again and seems to be getting a little closer. It's part of President Carter's program to get control of inflation. That's a good sign.

If you wonder why, after years of repeated defeats and rejections, the idea of a gasoline tax keeps reappearing, there's a simple answer. It's a direct and efficient way to discourage people from using so much of it. The tax returns a lot of money to the government. It ends the outrageous subsidy that present gasoline pricing offers to people who drive a lot -- a subsidy that has contributed heavily to the decline of the dollar over the past decade. The gasoline tax is a simple, sharp, useful too.Perhaps this is the year that the United States will finally begin to use it.

Mr. Carter has now imposed an import charge of $4.62 on each barrel or crude oil and gasoline coming into this country. He did it under his authority to control imports that threaten the national security. If every there was case of imports threatening the national security, the present flood of imported oil is it.

By a complicated administrative arrangement, Mr. Carter hopes to make the consumers of gasoline bear the whole burden of this charge. It's about 10 cents a gallon, and the only thing wrong with it is that it's too low. It is to hit the filling stations in mid-May. Meanwhile, Mr. Carter will ask Congress to replace it with a permanent tax, raising the federal gasoline tax from the present 4 cents to 14 cents, to go up in the future in step with gasoline prices.

In 1975, the courageous and foresighted House Ways and Means Committee reported a conservation tax that would have gone up only if gasoline consumption went up. It was defeated overwhelmingly in the House. But it's worth thinking about the difference that the 1975 bill might have made.

The country was importing about 6 million barrels of oil a day in 1975. Now imports are up over 8 million. But the Ways and Means Committee's bill also included machinery to pull oil imports down to 5.5 million barrels a day by this year. If American imports had been declining toward that level, it is utterly improbably that world oil prices could have doubled last year. It was only the massive and rising American demand for Middle Eastern oil that created the frantic seller's market in which the 1979 oil crisis took place.

Five years ago the price of gasoline was 56 cents a gallon, and the Ways and Means Committee's tax might have added as much as 23 cents to it. The rest of Congress thought it intolerably harsh and inflationary. It's true that thoughtful and informed Americans, of whom the Ways and Means Committee was a fair example, saw perfectly the kind of trouble ahead. But other Americans didn't want to hear about it, didn't want to think about it and, above all, didn't want to do anything about it.

Since then, of course, the price of oil, the price of gasoline and the inflation rate have all more than doubled. Hasn't the time come for a different and slightly more prudent attitude toward taxing gasoline?