Severance of tenancy SEV form

I'm going through a separation (not married) and we jointly own our home. I've been advised to sever the tenancy from joint to tenants in common.

I've been told to fill our SEV form and serve written notice to my ex partner (it is not amicable so am applying without him).

I need help please with the following - I've completed SEV form and it states "original or certified copy of the severance and my certificate are enclosed"
I have a letter to my ex which I can be left at their last known place of abode. But how do I prove that I've done this? Also, what is the certificate I need to include? As far as I'm aware, I need to send the SEV application form and put a copy of the notice of severance through his door. IS this right?

Any help is apprciated!

Hi Em - all noted and appreciated. So you need to complete panel 7 of the form SEV by choosing one of the options.
Based on what you have posted that's going to be Part C and it's then the second option that fits 
When we refer to 'certificate' that means your written statement beginning "I certify that ......" and you then complete it as appropriate as to what you did, left it at address X, and confirming that it hasn't been signed/returned for example
You don't have to 'prove' that you did it as severing the joint tenancy is in such a way is more about intent than you both having to agree and work together to apply.
So you send him your notice. And send us the Form SEV plus a written 'certificate' confirming what you did as mentioned

Thank you Adam, that's really helpful. Do I need to need to give my ex a copy of the application form or just the letter of severance?

Em - just the notice you have sent. The application form is yours, not his, but if you want to give him a copy you can. It has no impact on your own application

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