You can create a new rate in the system with the program B.T.W. Menu: System administration -> System administration financial -> B.T.W.
The third tab says 'Percentage'. Choose this low VAT rate. You then create a new rate with a +. Percentage and start date depends on.
On the third tab are the Percentage, choose this low VAT rate and with a + you create one with 9% and starting date 01-01-2019.