Vat Registration part way through year how to change vat status from Not Registered for VAT


I am having difficulty figuring out what steps I need to take to change from not registered for vat to now registered.  I have already gone into company preferences and ticked the enable MTD for vat box.  I have also gone into customer default settings and changes standard tax code to T1 20%.  When testing by raising a quote the sage program isnt adding VAT even with customer default seat at T1.  Am I missing something or will I have to delete the company and start again entering opening balances from this point from the existing data?