Hi there sylvia-reminisar,
Thanks for reaching out about your transactions. QuickBooks Online is a great tool able to help you keep track of sales and expenses so you know the amount of profit for your company. I can point you in the right direction to delete a transaction.
To delete a transaction already in your books, locate the transaction wanted by going to the Expenses tab. Once located, click on it to open the Edit menu, then in the bottom bar, click on More to Delete.
If this transaction is located in the For Review section in the Banking tab, you can select it by clicking on the Checkbox, then in the Batch actions, select Exclude.
If you have any other questions, feel free to reach out here.