Today, being 1st of November 2021; i created a sales invoice (copied from sales order) which was backdated to 20th of October 2021. upon checking P&L summary, i noticed the transaction reported on today’s date while the invoice date was 20th of last month. Please explain to me what i dont understand!
Not sure what transactions you are showing - what is COS/PZ?
It looks like this is the Cost of Sales account.
The inventory item was not in stock when the sale invoice was issued and so could not be booked to the cost of sales account. It would appear that you purchased the inventory item on 01/11/2021 and this is the date when the item cost could be transferred from inventory to the Cost ofSales account as shown in your list
If you check, you will see that the sale was indeed recorded on 20/10/2021.
At least that is all I can deduce from the limited information you have listed
