Customer screen > Account Details tab
Use this button so that the selected customer can receive a specific discount on a catalogue.
1.Click Add to add a new row.
2.Pick a catalogue from the drop down box.
3.Type a percentage in the Disc % column.
4.Click 
Update to save and close.
Catalogue discounts override any discounts set at a higher level. See the hierarchy below for details.
If you need to specify more than 1 type of discount you need to know the order in which they are applied. There is a hierarchy where one discount overrides the other.
The order goes from least specific to most specific:
•Product Discount •Discount Band •Catalogue Discount •Product Prices |