Anyone know how to edit an invoice that has been sent to a client? I need to amend it!

You've come to the right place, @BeccaW. 

There's currently no option to edit an invoice after it is sent to your client. However, you can manually update the existing invoice and re-send it. Here's how: 

1. Go to Sales from the left menu. 
2. Select Customers at the top. 
3. Enter the customer's name on the Search box. 
4. Locate and open the invoice. 
5. Make any necessary changes on the Invoice page. 
6. Click Save and send. 

You can also check out this article to learn more about managing your customers and income in the program. 

That's it. Feel free to post again here in the Community if you have other concerns, @BeccaW. I'm here to help.