User Activity

Can stamps be placed on polymailers/polybags ?Can it be used to replace envelopes for letter mailing?
A buyer purchase an item from me in Dec 2020, then in Jan 2021, buyer claims item not received.If I gave the buyer back a refund, for tax purposes do I write off the refund for Tax year 2020 or do I write it off as 2021?
As you all know there is a foreign currency exchange fee when paying with credit card or using paypal.What about using ebay gift card? Is there a fee?