If you have never used VAT at all, go into Setup - Tax types and change the 14% to 15%. Change the active end dates to somewhere in the future, say 2040.
If you can't change the percentage, setup a new tax type at 15% and use it. Change your default tax type for sales and purchases and you should be good to go. You will use the tax type report for reporting, as the new entries won't be setup in the tax box report. If you need assistance, you are welcome to contact me and setup a remote support session some time.