Warranties and guarantees
A customer has the same right to free repairs or a replacement regardless of whether they have a warranty or guarantee or not. So you may still have to repair or replace goods if a customer’s warranty or guarantee has run out.
Proof of purchase
You can ask the customer for proof that they bought an item from you. This could be a sales receipt or other evidence such as a bank statement or packaging.
You only have to accept returns from the person who bought the item.