Can I always require prepayment?

No — it depends on your industry and the kind of customer you're dealing with.

Prepayment from consumers generally has to be expressly agreed, and in some trades it's common to cap the advance at a small share of the total — around 10%, for example.

The rules vary by trade, contract type and standard agreements. As the business owner, you're responsible for knowing what applies to you. If you're unsure, check with your industry association or a legal adviser before enabling prepayment.