Ending of Tenancy agreement

Hello all, my tenant has recently signed a new tenancy agreement for another 12 month fixed period. Her circumstances have now changed and wishes to end the tenancy. Her sister is wanting to take over her tenancy and I am happy for her to do so.
Is there an easy way to do this change? Can I simply add the sister to the tenancy agreement, then remove the original tenant?
Many thanks

No, sign a new tenancy agreement with the sister, and sign a deed of surrender with the old tenant. The sister will NOT be taking over the existing tenancy, but signing a new one in her own right.

Have you referenced the sister?

Hi David, yes all came back clear!

Hi Karl, thanks for this. How do we sign a deed of surrendor? Is there a form on open rent?

No Deed of Surrender on Openrent. I’ve never had to do one, but sure an internet search will help, or check the pages of your Landlord association if you are a member.