Attention: Expenses linked to your payment card can't be deleted. You can only delete expenses created in-app by yourself.
Step 1
Choose expense
Step 2
Tap Delete this purchase.
Inside an expense, this option is found at the bottom.
If you don't see the options at the bottom, it is because the purchase is missing certain mandatory information (e.g. amount) which the app thinks you should add, and you will see a cross icon at the top right. Tap the cross, and you will see Delete this purchase option at the bottom.
To delete the picture of the receipt, see: Delete picture of receipt.