Only business sellers are allowed to make deductions.
Private sellers can't do this without reference to Ebay. Sellers can ask Ebay to step in and help, as buyers can.
How to ask us to step in
You can ask us to step in from the Returns & Refunds section of Seller Help. Simply select Take Action beside the item and then Ask eBay to step in.
Go to Seller Help
"There are two ways to be fooled. One is to believe what isn't true; the other is to refuse to believe what is true.”
Søren Kierkegaard, Danish philosopher (1813 - 1855)