Are your quotes clear? Often I see quotes using obscure part numbers and descriptions, designed for the MRP system, not for clear customer understanding. Do you customers really know what you have quoted them on??
Similarly, are your invoice item descriptions clear or are they written in manufacturer-speak? You payment can often be delayed as customers try to work out if they are being invoiced for what was received.
Make both invoices and quotes clear and it will benefit you and your customer!