Recurring invoices

This program accepts:

• Non-diminishing products, such as services, labour, surcharge or misc
• A product has 'Continue selling when sold out'

Parameters can be used to format the customer reference:

• [month] - to be replaced by the current/invoicing month, for example: Mar 2023
• [date] - to be replaced by the current/invoicing date, for example: 01/03/2023

Another example is: if the customer reference is set to "Service Maintenance - [month]"

then, when doing the invoice run in March, the customer reference will be "Service Maintenance - Mar 2023"