A SEASONAL NOTE: The Internal Revenue Service is, by all accounts, doing a far better job this year of processing tax returns and making refunds promptly. There is no sign of the gross confusion and turmoil in which it was entangled at this time last year. The IRS had been starved of money and of people for too long, and a steadily rising burden of paper finally got beyond its control last spring. This year the resources have been increased, and that part of the job is going much more successfully. But another part of it, compliance enforcement, still lags.

There's much learned dispute over the various estimates of the tax gap -- the incomes taxes that are never collected -- but the amount certainly runs to tens of billions of dollars every year. President Reagan says that the administration is considering a tax amnesty. In fact, as we have argued in this space, amnesty is a deeply damaging device and won't work as he thinks. What will work? Increasing the enforcement staff of the IRS, as the administration now proposes, but doing more of it faster than the administration intends. The present plan is to expand the number of revenue agents and auditors about 10 percent a year for each of the next three years. But the magnitude of the agency's responsibilities justifies a greater acceleration.

In relation to the number of returns, the service is less well staffed than a decade ago. Its recently improved computer systems certainly help. You should be aware that the IRS computers this year will match something like 95 percent of the income reports -- all those tiresome little bits of paper reporting interest and dividends and so forth -- with taxpayers' returns. But there are a lot of things that computers can't do. They can't judge whether a complex tax shelter is legal. They can't offer an opinion on the veracity of the return filed by a taxpayer who seems to be living extravagantly well on a remarkably small income.

Currently, the IRS is able to audit slightly over 1 percent of all individual tax returns. That's less than half the rate in 1976, and it's not enough. As it becomes notorious that a person's chance of being audited is very low, the temptation to play games inevitably rises. One former commissioner of the revenue, Sheldon S. Cohen, draws a parallel to the highway patrol. When motorists never see police cars on the road, the temptation to break the speed limit grows stronger.

How many auditors does the IRS really need? Nobody knows. So few returns are now audited that no one has any clear idea of what's being missed. All that you can say with assurance is that the right number of audits is quite a lot higher than 1 percent, and for every dollar spent auditing returns the country will get upwards of $10 in taxes otherwise left uncollected.