Section 21 – multiple tenancy agreements and gas certificates?

Hi everyone, I would really appreciate any sort of suggestions on what to do. I have had the same tenants for 10 years since 2013 and I want to move back into the property so I’m thinking of serving a section 21. I signed around 4 tenancy agreements over the 10 years.

I’m aware I need the gas certificate from when they first occupied the property (something I no longer have) but this was before 1st October 2015 when this was not a requirement. However, the tenancy agreements I signed post Oct 2015, I was slacking on gas certificates. I have the gas certificates for the last two years as well as the odd ones from previous years.

A new replacement agreement was signed at the start of this year where there was a gas certificate in place and given to the tenant.

So my question is, will my section 21 be invalid if I don’t have a gas certificate at the start for all the previous tenancies signed post-2015? Or does the one from when they first moved in and the one from the most recent tenancy be sufficient for a Section 21?

Thank you,

Kay