An election-minded Senate Finance Committee last night approved a bill to provide new tax breaks for business in so-called urban and rural enterprise zones, plus a bill to help investors by reducing from 12 months to six the holding period for capital gains.

These and other tax bills were approved following a morning session in which the Reagan administration said it will be at least a year before it will be ready to discuss any major restructuring of the individual income tax, such as the flat-rate proposals that have stirred interest on both sides of the aisle in the last year.

Probably neither house of Congress will have time to act on yesterday's bill before recessing at the end of this week for the election. But the bills will still be alive in the lame-duck session now planned from Nov. 29 to about Christmas Eve.

The president proposed creation of enterprise zones earlier this year, the one major new program he proposed to aid cities. The idea was to lure businesses to return to depressed urban areas by offering them special tax cuts. The committee bill authorizes creation of 25 such zones in each of the next three years. But because the committee has many farm state members, it required that eight of the zones each year be rural.

Inside the zones:

The existing investment tax credit of 10 percent would be increased, in some cases to 20 percent; the capital gains tax on certain property sales would be dropped; a 10 percent tax credit would be given to employers for additional wages paid to zone residents in any year, and a 50 percent tax credit would be given them for wages paid to disadvantaged workers.

In addition, federal agencies would be allowed to relax or drop non-statutory federal regulations inside the zones, although civil rights, minimum wage and most health and safety requirements would stay in force.

No cost estimate was provided on the zones bill, which would take effect next year.

Nor was one given on the capital gains proposal, under which profits from the sale of assets would qualify for capital gains rates, instead of the regular income tax, if the assets were held only six months instead of the current 12.

The maximum capital gains tax rate is now 20 percent, compared with 50 percent on ordinary income. Most beneficiaries of this lower capital gains rate are in the upper income brackets.

The new gains provision would also take effect next year. A similar provision was in the Senate version of this year's big tax increase bill, but was dropped in the House-Senate conference.

The committee also approved at least 10 other lesser tax bills in yesterday's session, probably its last before the members go home to campaign. These assorted lesser proposals would aid such beneficiaries as the Houston Chronicle, Westinghouse, the B. Altman department store in New York and three California utilities.

In the morning session, John E. Chapoton, assistant treasury secretary for tax policy, told the committee that the administration will not initiate flat tax or tax simplification proposals for at least one or two years. Among other things, Chapoton made the point that replacement of the current progressive income tax with a flat rate system would help those in higher brackets while adding to burdens in the lower and middle levels.

"A strong case can be made for a moratorium on tax legislation," Chapoton said. "The problems [with a flat tax] are severe."

Russell B. Long (D-La.), ranking Democrat on the committee, summed it up more earthily. "If you're rich, you'll love it," he said. "If you're not rich, look out."

Advocates say the tax code could be simplified greatly by moving toward a flat rate; some also say a flat rate would be more just than the progressive system, under which rates rise with income.

Treasury tables presented by Chapoton showed that certain flat rate proposals would cut taxes for those making $200,000 a year or more by 60.5 percent while increasing taxes for the middle and lower classes from 20 to 342 percent.