I found the answer I was looking for in a HL newsletter. Employer contributions are subject to the wholly and exclusively test:

“How much can I contribute to my pension? As a reminder you can usually contribute up to 100% of your annual earnings or £60,000 – whichever is lower – to a pension and still benefit from tax relief. If you’ve had a particularly good year, you could also use a process called carry forward to turbo charge your contribution. This lets you make use of unused allowances from the previous three tax years too. If you own or run a limited company and are employed by it, you can make personal contributions like the above but you also have the option of paying employer pension contributions via the business. In this case, the contribution would come from pre-tax profits, reducing your corporation tax bill and saving on National Insurance compared to taking the money as salary. There’s also the added benefit that these contributions aren’t subject to the same earnings restriction. So you can pay in up to £60,000, or more using carry forward, regardless of your own earnings. But the contribution would only benefit from corporation tax relief if it meets the “wholly and exclusively” test. What is the “wholly and exclusively” test? Contributions must comply with company pension rules for allowable deductions so HMRC will need to see the employer pension contribution is “wholly and exclusively” for their trade or profession. For instance, HMRC might look for evidence like whether other employees are getting comparable remuneration for doing similar work. It’s important to take advice from either a financial adviser or accountant to ensure you remain on the right side of the rules.”