https://esellercafe.com/ebay-sellers-may-pay-final-values-fees-off-platform-sales/
Sellers are liable for fees arising out of all sales made using some or all eBay Services, even if sales terms are finalized or payment is made outside of eBay.
Sellers are also liable for final value fees if they offer or reference their contact information, or ask for a buyer’s contact information, in the context of buying or selling outside of eBay, even if the item does not sell.
While eBay has been warning sellers about off-platform sales or discussing off-platform sales with buyers, the company is taking an another significant step into enforcing this issue.
Previously, eBay announced that all sellers must remove contact information from their listings, including phone numbers.
With this new policy in place, your only protection from being charged for a sale that may or may not happen outside of eBay is to report a buyer asking you for making just such a sale.
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Basically, it sounds like ebay wants *all* communication to go through their messaging system. No more calling a retail seller to ask questions or whatnot.
It also sounds like if a buyer contacts a seller about buying something outside of ebay, the seller will get hit with the final value fee if the seller doesn't report it to ebay.