Since Small Transfers doesn't store customers' funds or allow them to withdraw a balance, the platform is not considered an e-money institution or a "wallet".
When the customers pay their balance, we immediately forward the funds to the merchants.
What happens when the charge attempt fails after initial preauth?
If a merchant successfully authorizes a charge, the amount is reserved for that merchant for a limited period. Trying to capture that amount (or less) during this period will succeed.
Details: https://smalltransfers.com/terms