1- In case of invoices for the entire sales order at once (one invoice):-
The creation of a new sales invoice must be rejected if its value or quantity of items is greater than the value or quantity of the sales order.
2- In case of invoices for the sales order on more than one invoice (several invoices):-
The creation of a new sales invoice must be rejected if its value or quantity of items is greater than the value or quantity not invoiced for the sales order
3- And from the sales orders tab when it is copy to anew sales invoice, it will be with the quantities and the remaining value that not invoiced from the sales order
4- And the same suggestion applies to purchase invoices.
I believe there is no justification for any of these suggestions, and many valid reasons why they should not be implemented. Can you furnish a justification for even one of the suggestions that applies to a general purpose accounting program used in many types of businesses and under many workflows? In other words, is there a reason to disallow other users’ practices just to suit your individual preferences?
So what if it is lower? Same argument applies for your other points. Please note that it is perfectly normal that Sales Invoices differ from the quantities and values listed in the Sales Order. Some reasons:
Partial shipments or deliveries.
Discounts or price adjustments.
Backorders.
Returns or damaged goods.
Currency fluctuations.
Additional charges like handling fees.
Same applies to Purchase invoices.
So unless you can answer @Tut it may not be useful to pursue this further.
Your post was clear. You made four suggestions. When asked to justify even one, you instead asked forum members to read your post again. You got two quick responses. You are unlikely to get anything further unless you answer the question asked.