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Before money moves, check the identifier
Most marketplace fraud is caught by looking at identifiers that are expensive to fake: the payment handle, the account age, and whether the same identity appears on more than one platform with consistent history.
A username is the cheapest of those checks and the one most people skip. Run the seller handle before you send anything, and look for how long it has existed rather than what it claims.
Reading the signals on a payment handle
Payment handles — cashtags on Cash App, usernames on Venmo — are globally unique and effectively permanent, which makes them the strongest identifier in a transaction between strangers.
Open the payment page and read the display name. If the name on the payment handle does not match the name used in messages, that mismatch is the finding. Stop there and ask why.
Checks that catch most bad sellers
Account age plus evidence of completed sales. A profile created two weeks ago selling a high-value item at a suspicious discount is the classic shape. Look for reviews that span months, not a burst of five-star comments in one week.
Photo provenance. Reverse-image search the item photos. Sellers who lift images from other listings, stock sites or other people's posts are usually not in possession of the item.
Platform discipline. Take the transaction through the marketplace's own checkout when one exists. Every request to move to direct payment removes your protection.
The buyer side matters too
If you are the seller, the same checks run in reverse: a brand-new buyer account pushing to pay outside the platform, or overpaying and asking for the difference back, is running a known refund-fraud pattern.
Both directions share one rule — keep the payment inside a channel that can reverse itself, and treat urgency as a warning rather than a reason to move faster.