How do I confirm an F10 was notified to HSE for a domestic conversion?

I want to check HSE were notified when my home was converted last year. The project would have been notifiable due to length of schedule and hours to complete.

As a domestic client, under CDM 2015 section 7, the duties in relation to notification would be carried out instead by the Contractor (or possibly designer). The notification would usually be made via the HSE online form (see following link)
and there would be a ‘serial number’ issued to enable the form to be accessed.

The Contractor who undertook the works would most likely submitted this so you could ask if they can provide you with a copy of the F10 form.