In theory, an employer can pay any amount of pension contribution to a registered pension scheme in respect of one of their employees or an ex-employee, regardless of their salary.
Employer contributions qualify for full corporate tax relief, assuming they meet the 'wholly and exclusively' requirements.
HMRC Pensions Tax Manual - PTM043000: Contributions: tax relief for employers
Employer contributions usually benefit from full corporate tax relief in the accounting period in which they are paid. However, if the employer pays a pension contribution that's more than £500,000 of what's been paid in previous years, they may have tax relief spread over a period of years.
HMRC Pensions Tax Manual - PTM043400: Contributions: tax relief for employers: spreading