The administration's latest tax plan would have almost the same impact on business taxes as its original proposals, if the years from 1981 to 1986 are taken as a whole. However there are some changes in the distribution of the curs, and they would be smaller in the early years than under the original program.

The plan sent to Congress this week would cut business taxes by $2.1 billion in fiscal 1981 and by $9.7 billion in 1982, rising to $65.6 billion by 1986. For the years from 1981 to 1986 the new proposals are just $3.6 billion smaller than those in President Reagan's first tax plan announced on Feb. 18.

Last week the president had announced a bigger cutback in the tax breaks he had proposed for business, but he backed off from that after business complaints. And although the latest plan gives smaller breaks to businesses between 1981 and 1985 than did the original proposals, by 1986 the business tax cut now proposed is $5.4 billion bigger than in the February package.

Business leaders yesterday seemed generally in favor of the new proposals, and the Chamber of Commerce and the American Business Conference Inc. endorsed them. The administration was assured of support from the National Association of Manufacturers on Tuesday and from the Business Roundtable on Monday.

The accelerated cost recovery system which has been at the heart of all of the administration's business tax proposals would allow for swifter and more generous depreciation of investments than under current law.

The 10-5-3 depreciation proposal would shorten the write-off period for many investments and allowed faster write-offs in early years. A "double declining balance" calculation in the original plan would allow business to write off twice as much of an investment in the first year as would be allowed under straight-line depreciation. The remaining balance in each year is written off twice as quickly as under the straight-line method, so that the balance dwindles rapidly with smaller write-offs in the later years.

The new plan provides for only 150 percent early write-off between 1981 and 1984. This cuts the business benefit by $600 million in the current fiscal year, $2.9 billion in fiscal 1982 and rising to a peak of $8.8 billion by 1985.

The administration now proposes a 175 percent write-off for investment undertaken in 1985 and restores the double-declining-balance or 200 percent, system from 1986 onwards.

Other changes from the February proposals both add to and subtract from the cost of the original 10-5-3 depreciation plan. There is more flexibility for business to choose between a faster write-off or a straight-line write-off.

In addition, Reagan now proposes:

To let all investment in buildings be written off in 15 years and use a 200 percent accelerated write-off, rather than straight-line depreciation. This adds $1.7 billion to the bill by 1984 and $2.2 billion by 1986.

To eliminate a deduction for investments which take a long time to build and which are in progress for a number of years. The qualified progress deduction allows firms to write off some of the cost before the investment is in place and ready to be used. The elimination saves the administration $2.2 billion in fiscal 1982, $4.4 billion in fiscal 1984 and $4.6 billion in the next two years.

To liberalize leasing requirements for the corporate sector so that lessors would have to own 10 percent rather than the present 20 percent of equity in leased equipment to benefit from acclerated depreciation write-offs. In addition, the cash-flow rules for determing what is a true lease would be liberalized. These tax benefits would then, Treasury presumes, be passed on to the lessees.

Firms who would not be able to take all their depreciation deductions -- for example if they do not make enough profits against which to write off their costs -- now would be able to lease rather than purchase equipment. Steel and auto companies and other with low profitability would be helped by this provision. It would cost $2.7 billion next year, rising to $5.4 billion in fiscal 1984 and $9.4 billion in 1986.

The total depreciation package costs $8.9 billion in fiscal 1982, rising to $41.9 billion in 1984 and $63.9 billion by 1986. The original depreciation proposals would have cost $60.2 billion by 1986.

The other business tax changes now proposed by the president are:

A 25 percent investment credit for wages spent on research and development, costing $400 million in 1982 and $700 million in 1984 through 1986.

Liberalization of the earlier tax plan for foreign investment, which in the original bill would have toughened the tax laws on companies with foreign assets.

An investment tax credit for rehabilitation of old buildings.