Claiming Pre-Registration VAT.

Hello Mob28, 

Welcome to the Community page, 

So all you would need to do, if this is your first return in QuickBooks and you wish to claim back pre registration VAT is  adjust the VAT to include the amounts you need. We've included a help article here on how to make adjustments in QuickBooks Online. Any questions on the steps to make an adjustment please feel free to ask them here. We'd be happy to help you further.