VAT and land sale

[JETSET]

Evening,
I am running a company down and need help with vat deregistering.
Last month I had 2 sites (land), one I reversed the option on as owned for 25 years, the other owned 15 yrs and opted. I have just completed on the sale of this one, submitting vat invoice and want to now deregister. As I have raised a vat invoice I guess I should pay this over? (Unless I can avoid?). The other site has been rented out now for over a year with no vat charged, turnover £20k. Any worries about comeback?
Andrew

[section 44]

Unless I can avoid?)

Evade?

If you have charged VAT then that must be accounted for to HMRC. I'm slightly surprised that you think it might be optional - if so then wouldn't all businesses simply trouser the VAT and boost their turnover by 20%?