By sector
Courses billed by hour, by student or by session, with VAT and withholding tax properly reflected.
Quote and invoice the way you actually deliver your course.
Monthly or quarterly programmes that prepare themselves as a draft.
Each line with its own VAT rate; withholding applied if it applies.
A company with several departments that pay separately, without duplicating the client.
Heads up: If your training is VAT-exempt, mark it on the line; check with your accountant which regime applies to your courses.