The only thing worse than a two-day hangover is the arrival of "Form 1040a, Federal Income Tax Form and Instructions." If ever there was a more definitive harbinger of the New Year than Uncle Sam's annual reminder that it's time to pay up, it has escaped my knowledge.

And it's also time to remember Children's Hospital. You know, the one on Michigan Avenue with the "built-in deficit" that is an unavoidable part of providing free or low-cost medical care to needy children. The one where the patient's health comes first, and the problems of payment come much later.

Speaking of later, if you help out Our Town's foremost pediatric facility with a contribution now, later you can apply that charity to the bottom line of your income tax calculations. On page 4 of Form 1040A, one of the specified types of deductions is "gifts to churches, charities, and similar organizations." We qualify.

If I try to discuss income taxes anymore, I'm sure to get into trouble, and since we're still fighting an uphill battle against the "built-in deficit," let's get on with the business of the day.

Several anonymous letters bear repeating this morning.

One, with a check for $28.25, explained that that sum is 13 percent greater that $25, which was the writer's contribution last year. That's about our annual inflation rate, and the percentage above last year's total of roughly $231,000 we need to provide the same amount of curing power at Children's that we did last season.

The other letter brought $32 from parents who sent $23 last year.The explanation was that their new daughter measured 23 inches last December, and she is now 32 inches tall. That's an interesting formula.

Finally, a check for $1,000 arrived from the daughter of a former medical chief-of-staff at Children's Hospital in memory of her parents. She said, "I feel this contribution will help all the marvelous work being done at Children's. Also, it is my great love of all children that gives me pleasure in sending you this contribution."

Also joining the fight today are several area groups and employers.

The New Horizons Bridge Club collected $10 for the needy young patients at our hospital. What appears to be the fifth and final installment from the George Mason University Cross-Country Team totaled $15. The last remaining member of that fine group graduates this year. Good luck and so long!

And out-of-town company, United Luggage & Camera Shop Inc. of Springfield, Mass., sent $25. A check for $30 came from the sixth graders of Clifton Elementary School. They declined an in-class gift exchange in favor of Children's Hospital.

The Office of the General Counsel at Communications Satellite Corp. held a Christmas lunch and collected $50 more than they needed. I have that $50 now. The writer said it was not necessary to acknowledge their group gift, but I hope that Comsat's example will prompt similar responses from other area high technology firms.

Gallery 324 of the Old Town Art Co-Operative Inc. sent $52.83 for victims of neurofibrilmatosis. For the fifth consecutive year, the ladies of the Benefit Bridge Club in McLean played cards for Children's. They pay a penny for each missed trick, and they went down 5,500 tricks according to their check for $55.That's a lot of water under the bridge.

Employes of Mrs. K's Toll House, a restaurant in Silver Spring, sent $56 on behalf of their employers. A check for $77.80 arrived from the Shooter's Hill Carollers, "who very nearly broke their necks sliding around Shooter's Hill on Christmas Eve, as they have done for the past twleve years."

There's just enough space for the quadruple-digit winner, and the honor goes to 68 employes of The Chalres E. Smith Cos. in Arlington. The $1,605 in checks, they wrote, "represent a continuing tradition of making a contribution to Children's Hospital in lieu of exchanging Christmas cards." The gift concluded a decade of concern that began in 1970 with $92 from seven folks there.

So, 77 individuals contributed $3,481.25 and our 10 groups added $1,976.63 for a daily total of $5,457.88. Inasmuch as the shoebox held $76,122.19 yesterday, it now contains $81,580.07.

Please send your tax-deductible check, made payable to Children's Hospital, to: Scott Chase, c/o The Washington Post, 1150 15th St. NW, Washington, D.C. 20071.