situation if i have to repay deposit x 3.

Possession - Section 8 and Section 21

I have issued s 21 to end a periodic agreement and tenant is saying I didnt register a deposit whereas on tenancy agreement it states 2 months rent paid in advance.
Whilst I am 99% sure that my case is correct and can prove no deposit was paid. I wanted to know what the position of the actual tenancy if the courts rules that there was a deposit. I'm aware of penalties of 3 x deposit etc but wondering what happens after that and what if any procedures can be used to remove the tenant and timescales.
Any information would be helpful