If you unintentionally purchase more cryptocurrency than you meant to, you can follow the steps below to immediately sell your crypto for cash. The funds will be credited to the cash balance in your Coinbase account, where they will be available for future use or to cash out.
From a web browser:
Click Buy / Sell.
Select the asset you want to sell and enter the amount.
Click Sell [asset] and confirm your selections.
Click Sell Now to complete the sale.
From the Coinbase mobile app:
Tap the menu in the upper left corner, then tap Sell.
Tap the asset you want to sell and enter the amount.
Tap Review Order and confirm your selections.
Tap Place Order to complete the sale.
Once the action is complete, the funds will be available in your cash balance (USD balance, for example).