Millions of Americans will receive an unwelcome New Year's present when the government increases the amount of earnings subject to Social Security taxes and federal employes begin paying 1.3 percent of their salaries into Medicare for the first time.

The new year brings some bad tidings for just about everyone as cigarette taxes double, telephone taxes triple and even the cost of a passport jumps from $10 to $35.

These are among the new tax laws, benefit rules and regulatory changes that take effect today.

But the increase in the federal gasoline tax from 4 to 9 cents a gallon will not be felt until April 1.

And the take-home pay of most Americans should increase in July, when federal income tax withholding is reduced in the third and final year of the Reagan administration's tax cut.

The most politically sensitive change is probably the Social Security tax increase, which comes at a time when the Reagan administration is trying to decide whether to seek further tax raises, reductions in future benefits or some combination of the two.

Today had been the deadline for a presidential commission to recommend ways to shore up the financially troubled Social Security system, but President Reagan gave the panel a two-week extension after its members failed to reach agreement.

The Social Security levy will remain at 6.7 percent of taxed earnings this year.

It will not be raised until New Year's Day, 1985, when it rises to 7.05 percent. But, beginning today, the amount of each worker's earnings to be taxed increases from the first $32,400 of annual earned income to $35,700.

Everyone getting $32,400 or more in 1982 paid $2,170 in Social Security taxes. Everyone getting $35,700 or more this year will pay $221 more, for a total of $2,391.

The increase in the wage base, which will affect about 9 million taxpayers, is produced by a formula tied to national growth in wages and benefits, and it increases automatically in future years.

This also applies to the new Medicare tax on federal employes, most of whom are eligible for Medicare benefits. They will now pay the same 1.3 percent rate as private workers, Social Security spokesman John Trollinger said. This amounts to $260 a year for a worker getting $20,000, he added. "I should know that, since it comes out of my paycheck," Trollinger said.

In other Social Security changes, workers over 70 now can earn unlimited amounts without losing any benefits. Those 65 to 69 can get $6,600 a year before their benefits are reduced, an increase from $6,000 last year. And most firms now must give workers 65 to 69 the same health insurance as given their other employes, leaving Medicare to pay only certain expenses not covered by company policies.

Federal excise taxes on cigarettes jump from 8 to 16 cents a pack today, while the tax on telephone calls goes from 1 to 3 percent. Both increases are part of the $99 billion tax increase that Congress enacted last summer.

The passport fee, which had risen only a dollar since 1932, is being more than tripled to $35. There is also a $7 surcharge for anyone who has not had a passport for eight years, can't find an old one or was under 18 when it was issued. However, the new passport will be good for 10 years instead of five.

The Internal Revenue Service has made a number of changes in the tax return for 1982, which taxpayers are receiving in the mail.

Working couples can avoid the so-called marriage tax by deducting 5 percent of the salary of the lesser-earning spouse, up to $1,500, which increases next year to a 10 percent deduction up to $3,000. For a husband getting $15,000 and a wife making $13,000, the IRS says, the new law cuts about $500 from the 1982 tax bill.

People receiving private pensions or annuities will find some of the money automatically withheld for taxes this year, unless they specifically request otherwise in writing. An IRS spokesman called this "an area of fairly low compliance," meaning that some of the retirement income isn't being reported by taxpayers.

In another "area of low compliance," waiters, waitresses and bartenders will have to keep more careful track of their tips starting today. Those who don't acknowledge tips amounting to at least 8 percent of their salaries will be taxed on that amount, based on wage statements to be submitted by their employers. Dealers in Atlantic City and Nevada casinos are not covered by the new policy.

Another new IRS rule, requiring that 10 percent of stock dividends and bank interest be withheld for taxes, will go into effect July 1.

In other changes, beneficial to some taxpayers, the maximum deduction for child care will increase from $400 to $720 for one child, although the care must be necessary for a parent to keep a job.

Finally, in a rare bit of luck for some taxpayers in the new year, anyone owning a stripper oil well that pumps fewer than 10 barrels of oil a day today becomes exempt from the "windfall" profits tax on crude oil.