It is not mandatory to submit your statement to TISCreport. However the Home Office have asked companies to register with us because we're helping with their planned audit on the 31st March 2019. As a result a vast proportion of companies with existing compliance statements (with similar letters) are setting up accounts on TISCreport so that they can submit their statements and statement URLs as proof of compliance against their company numbers.
Once you do so (you will need to subscribe to a membership account, which can be done for free), we will be publish your statement with a high level of confidence on your public TISCreport profile. You will also be able to check your suppliers' compliance using the free dashboard you get access to as an affiliate member.
If you haven't already checked the resources provided by the Home Office to ensure that your statement itself is compliant then it would probably be a good idea if you did so. A vast number of companies have interpreted Section 54 differently, and you'll find the guidance provided really helpful.