Whether you can cancel a withdrawal depends on how far it has progressed.
If the withdrawal is still Processing
Contact live chat immediately. If the transaction has not yet been broadcast to the blockchain, the support team may be able to cancel it.
If the withdrawal has been sent
Once a transaction is broadcast to the blockchain it cannot be recalled. Blockchain transactions are irreversible. If the funds were sent to the wrong address, see: I sent crypto to the wrong address.
How to avoid mistakes before confirming
Always double-check the destination wallet address and network before confirming a withdrawal. The cashier shows all details on the confirmation screen before you submit. Take an extra moment to verify the first and last few characters of the address.
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How to withdraw from Flush
My withdrawal is not showing in my wallet
I sent crypto to the wrong address