Objective : For Finance team to rectify the content for the billing.

Targeted Audience : Finance Team

UI : Same as Add UI.

Requirements :
1) Customer Invoice can be edited as long as the status is New, Confirmed or Billed (including overdue).
2) When Status = New, invoice can be edited without any further action.
3) When Status = Confirmed / Billed, 2 scenarios to cover
Scenario 1 : Before current accounting period end, update existing invoice.
Scenario 2 :
- After current accounting period end, upon editing of invoice details, system shall update existing invoice as Cancelled and create a new invoice as "New" status. The old invoice no that has been cancelled shall in bracket under the Invoice No column in Listing Page, Edit and View Page to indicate to user that it is an edit after accounting period.
- On the backend, system shall auto create a CN record to offset the values for old invoice and create a new DN record to register the new value for the invoice.

Estimated Effort for 1st draft for FO : 6hrs
Internal Effort Estimation : 4hrs