Employers will pay substantially higher premiums for government pension insurance for single-employer pension plans and will find it more difficult to terminate such plans under provisions included in the budget reconciliation bill just signed by President Reagan.

Under the bill, the annual premium paid by a single-employer pension plan to cover government insurance of the benefits against plan default will rise from $2.60 a year to $8.50, according to an analysis by Buck Consultants Inc., a large actuarial and employe-benefit consulting firm. The increase is effective for plan years beginning after Dec. 31, 1985.

The Pension Benefit Guaranty Corp., the government agency that runs the pension-insurance program, in which participation is mandatory, had warned that, unless the premiums were increased, it would not have enough money to pay the pensions of workers whose pension plans collapsed or otherwise were unable to meet their obligations.

A single-employer plan is one in which a business runs a pension plan limited to those employed by that business.

Multi-employer plans, by contrast, are run jointly by a union and a number of different employers in the same industry, such as the construction trade.

About 30 million workers are covered by single-employer plans and about 8.5 million by multi-employer plans, according to the PBGC.

Other provisions of the same bill are designed to make it harder for firms to terminate single-employer plans and "dump" their future obligations on the PBGC insurance system, a practice bitterly criticized by PBGC Executive Director Kathleen P. Utgoff, who supported the legislation on behalf of the administration.

Under the new law, to terminate a plan, the employer would have to show in various reports to the PBGC that it had put aside enough money to pay all benefit commitments, or that the firm was in financial distress.

To establish financial distress, the firm would have to show one of the following: that it was in a liquidation proceeding; that it was in a bankruptcy reorganization and the court had approved a plan termination; that it would be unable to continue in business unless the plan were terminated; or, according to Buck, that it had experienced unreasonably burdensome pension costs "solely as a result of a decline in the work force."

Even if allowed to terminate its plan, the distressed firm would not be off the hook unless it had put aside enough money to meet future plan commitments. If it had not, the firm still might have continuing future liability for obligations incurred up to the time of the termination.

Also under the bill, an employer spinning off or selling subsidiaries and transferring unfunded pension liabilities as part of the transaction could be responsible for the unfunded benefit entitlements if a distress termination occurred within five years (excluding any improvement in benefits after the spinoff or sale), according to Buck.

Another provision of the bill will increase health insurance costs for employers with active workers over 69 and their spouses.