When handling changes of VAT, or Media Campaigns/Items that run over different VAT validities, there are different options available within ADvendio.
...
Prevent overlapping VAT/GST rates
VAT rates generally run on a yearly basis, in order to prevent Media Campaigns and Campaign items from potentially overrunning different VAT rates, you can 7.2.2.6 Sell by fiscal year only . To do this, simply go to Administrating Settings and set Prevent Fiscal Year Overlapping to True. Doing so will reduce the risk your items will overlap different VAT settings
...