This field contains the invoice discount amount that was calculated on the line if you clicked the Functions button and then clicked Calculate Invoice Discount. If you have placed a check mark in the Prices Including VAT field, the amount displayed will include VAT.
The discount will be calculated automatically if there is a check mark in the Calc. Inv. Discount field in the Sales & Receivables Setup window and you do one of the following on the sales document:
Click the button that has the name of the particular document type, for example, Invoice, and then click Statistics.
Click Posting, Test Report.
Click Print.
Post the document.