NOTE: This option is for TNG version up to 1.0.6.5, also see Can I add a markup to TNG?
TNG does not have a markup % feature, you can use the following:
The VAT Factor field on the General Settings page can be used to add a extra Markup over and above the VAT with the following formula:
VatFactor = (1 + VAT/100) x (1 + MarkUP/100)
For example:
Vat = 14%, Markup = 50%
VatFactor = (1 + 14/100) x (1 + 50/100)
VatFactor = (1+0.14) x (1+0.5) = 1.14 * 1.5 = 1.71