i guess they cant backdate it, my contract says it will be no more than the monthly payment, I'll file it in a safe place
To be honest, I'd either read up on the scheme or burn the contract or, preferably both. In fact, if it is as you say, do yourself a favour and never mention the contract to anyone "official" who asks about it, because the contract, if it is as you say, will actually increase your tax charge. I'm feeling charitable so I'll summarise problems with your post.
First, HMRC could back date it if they wanted.
Secondly, they don't have to backdate it, because the scheme rules have always said that the sale must be at market value or it will be a taxable benefit.
Thirdly, the company can charge what they like, but the difference between the sale price an employee pays and the market value of an asset will always be a taxable benefit.
But fourthly, and most critically, if there is any form of agreement about the sale price in the contract, it is not a rental contract but a hire purchase contract and the whole thing is taxable anyway.
So, please, if you do want to file the contract in a safe place, make sure it stays there.