With a few fee reductions and tax credit increases acting as a cloak of sorts, the District government has approved a $69.1 million revenue package composed primarily of one-time-only windfall revenue.

The revenue package, which Mayor Walter E. Washington into law week, contains significant reductions in the cost of automobile licenses, increases in the amount of deductions allowed some city residents and an increase in the eligibility ceiling for property tax relief under the city's "circuit breaker" tax credit plan.

Yet the same package is being used to plug anticipated gaps in the city's $1.2 billion budget for the fiscal year beginning in October by simply shifting the payments dates of several taxes into that fiscal year instead of the next.

Council member Marion Barry (D-at large), chairman of the finance and revenue committee of the council. "But we didn't have a choice if we wanted to hold down taxes."

It's kind of like saying to the taxpayers, here, we've got a gift for you. It's a Trojan horse," one city official said privately. "It looks good this year, but next time around it will come back to haunt you."

The fee reduction that is likely to affect the most city residents are $15 and $20 reductions in auto license fees that will become full-size cars, like Cadillacs, Oldsmobiles and Ford Ltd's, whose annual registration fee would drop from $96 to $76. All other auto registration fees would be $15 cheaper. Tha means $35 instead of $50 for subcompacts like Vega and Volkswagen; $42 instead of $57 for compacts such as Maverick and Nova; and $68 instead of $83 for mid-size models like Chevelle and Torino.

Many District residents will also benefit from changes in the deduction allowances for District income taxes. New provisions in the revenue package will for the first time allow alimony payments to be subtracted from gross income without itemizing all deductions and having to fill out the more complicated "long form." All medical expenses in excess of three percent of the adjusted gross income will also be deductable.

Present city tax laws allow parents to only claim child care payments as a deduction from their income. Under a new provision of the revenue package, however, parents may use some of the money paid for child care as a tax credit - an actual subtraction, from the amount of taxes they pay.

But the new tax plan will allow parents to take up to 6 per cent of their child care payments (of up to $2,000 per year) and subtract it from the tax bill. For a family of four earning $15,000 per year that now pays $630 in D.C. tax, that would mean $90 less in taxes if the family paid $1,5000 in child care payments.

Another tax credit included in the revenue package is the "circuit breaker" property tax credit, which tries to link the amount of property tax paid to the income of property owners and renters and is designed to benefit lower income families.

The circuit breaker system, which was first used in 1975, allows tax credits of up to $400. Previously, no persons with incomes of more than $7,000 could benefit from the plan. The new revenue package raises the ceiling to $10,000. Thus, a person with a $21,900 house (whose property tax would be $400 per year) would save anywhere from $16 (if the income were $9,500) to $342 (if the family income were $2,000).

For renters, the tax credit is based on a formula which equates 15 per cent of the rent paid with property tax. Thus, a family paying $222 per month rent would receive the same tax credits as property owner paying $400 in yearly property tax.

One fee increase in the revenue package is the institution of a user fee for ambulance service which is now free The fee, which is to be set by the mayor, will probably be $35. City officials believe 96 per cent of the fees will be paid by insurance companies and the law forbids denial of service for inhability to pay.

The ambulance fee provision is expected to generate $400,000 per year. The package also contains an increase from $5 to $8 per ton for the cost to commercial trash collection firms for dumping at city dumps. That measure is planned to raise an additional $800,000.

The bulk of the money to be raised in the revenue package, however, comes from the one-time shifts in payments schedules, which will mean that money ordinarily not set to come in until the 1979 fiscal year will come in during fiscal 1978 instead.

Gross receipts taxes on banks, savings and loan associations and utility companies will be due in one July 30 and March 31. Property taxes from large property holders - persons with real estate liabilities of $100,000 or more - will also go to a one-time only payment schedule. Those taxes will be due on Sept. 15 rather than in two payments on Sept. 15 and March 31.

The city also hopes to gain an additional $20 million by advancing the collection dates for federal water and sewer payments. Former President Ford has recommended in his proposed 1978 federal budget that such an advanced payment schedule be undertaken.