The 'Valid From' field retrieves the date set in the Shipping Advice (CSA) Document earlier in the process, if not a ValidFrom value is set manually. 

This date sets the start date of the rental plan, and when it is activated (set to ST:4) it means the plan has started and will no longer be open for editing. Edit the start date while the COP document is in ST:1 - ST:3:

1) Open the desired COP document.

2) Locate the ValidFrom field and press the calendar icon.

3) Find the desired start date and press it.

There is an F12 option: Change Validfrom.

This opens a pop-up where the 'Valid from' date can be changed.

An error message appears if an invoice has been made on the Recurring Invoice Plan (COP).