There are two reasons for buyer returns.
The first is Not As Described.
With this eBay expects the seller to provide return postage.
The second is Buyer Remorse.
With this eBay expects the buyer to pay for the return.
Now.
Life is not that simple.
Has the buyer opened a Dispute? (You don't want him to.)
If he has, what reason did he choose?
If it is Buyer Remorse and this: The part did not fit the buyers vehicle
indicates this is Buyer Remorse, then he returns the part on his own dime. While a buyer is smart to use a tracked service, a good seller doesn't worry about it.
The part arrives, you refund. You try to be polite about it all.
But.
He sounds grumpy already. And yes he's blaming you for his mistake.
You try to be polite about it all.
Because if he opens a Not As Described dispute you are forced to pay for return shipping - with tracking- and you are on eBay's radar over the refund.
You don't want that.
Not every transaction will go smoothly.
And here's the further complication.
Is he is Canada?
Please please please say he's in Canada.
Because then you can send a Canada Post shipping label to him quite easily and when it returns to you, you refund.
Done and you try to be polite about it all.
But if he is in the States, it has until recently been impossible to send a shipping label and we needed workarounds.
It seems recently that possibly we might be able to send USPS shipping labels to our American complainers using Shippo. We have to register with them to use USPS shipping.
No one has reported doing this yet, so I remain unconvinced.
TL/DR
Pay for the return shipping. Save hassle. Try to be polite about it all.
