In Belgium the cash discount (= escompte/korting) is quite specific.

 
The cash discount impacts the basis to calculate the VAT amount and the basis itself.
If we take the following example:

 
You sell goods for 1.000€ VAT Excluded
You give 2% cash discount to your client if he pays you during 7 days after the invoice date.

 
The following calculation has to be done: 

When you create the invoice the following entry is generated:

CASE 1) The client pays you during the week after the invoice date ( = so the client can benefit from the cash discount)

CASE 2) The client pays you after the 7 days