Declaring Company Pension Contributions on SA Tax Return

Hoping someone maybe able to offer some guidance on this, my accountant suggested a while back that my pension was something I should discuss with an IFA but I've been investing in a Vanguard SIPP.

How do I declare my company pension contributions to HMRC? I can't see a section for company contributions on my SA Tax Return, only personal contributions. Am I missing something on the return, is there another means of submitting the information or does it go via the SIPP provider?

I thought a Google search would easily answer this but I'm not having much luck so any suggestions gratefully received.