Updating equity amounts in shared property

My wife and I co-own a property with her mother. The equity amounts were registered when we submitted a TR1 when we initially bought a share in the property. Since doing this we have increased our share of equity in the property by roughly 5%. We would like to update the details as we are shortly planning on selling the property, and would rely on the updated equity amounts to divide up the proceeds of the sale. 

It’s not clear to me how we could update the deeds as the TR1 doesn’t seem appropriate for these purposes and nor does the TP1. Can anyone advise me how we can go about doing this?

 

David - we don't register or record the equity amounts/shares. Whilst you might include such details in the initial Transfer into your joint names and apply for what's known as a form A/joint proprietor restriction we don;t add % shares to the register or update records thereafter. 
Joint property ownership: Overview - GOV.UK
If you have altered your % shares then that's a private matter between the three of you