Discount on Sales Invoice after submit

Dear all
i need to make a discount on sales invoice after submit without cancel the invoice or sales order
can any body help me ?

Use Credit Note in Journal Entry against that Sales Invoice for discount amount.

Sales Discount A/C debit
Customer A/C credit (with respective sales invoice)

thanks for your replay
can you send me the steps

Create a Journal Entry of type Credit Note, refer the screenshot below:

Choose the appropriate Customer and then, expand the second row(Customer’s Row) and select the appropriate Invoice against which you want to give discount for.

Thanks @harshit-30 for your effort

if i choose credit not then invoice selection is empty

i have the same of this…
it need the invoice to be “Return” to show up on the filter here!

any workarounds for this ?