Mark as sent
Once your invoice is sent to a client, switch the status of the invoice from Unsent to Sent and put down the sent date.
The invoice changes it's status to Unpaid.
Activity
Activity tab shows you everything that was going on with this invoice chronologically. You can add comments and discuss this invoice with other people.
Add subscribers
Add people to the invoice that needs to be notified when something happens with an invoice - someone leaves a comment, adds a discount marks invoice as sent or paid, etc.
If you need to remove a subscriber from an invoice, just hit the x next to a subscriber. That person will no longer receive any notifications on this invoice.
Add tags
Add tags to your invoices for easier organizing and filtering.
Go to budget
You might want to take a look at the budget the invoice was created from. Click on the menu and select Go to budget option.
Delete invoice
Click on the menu and select Delete option.