From your ZenMaid dashboard, go to Scheduling. You may use the calendar view you prefer.

Click on the appointment until the appointment details window pops up to your right.

On the sidebar pop-up, click the Actions button and select Invoice customer.

A new pop-up window will appear, where you'll see that invoice has already been issued.

Click on the Action button, and choose Void invoice.

There will appear a message that says "Invoice voided!"

After the invoice has been voided, go ahead and create a new invoice, the same way you did it last time.

There you will be able to make any changes you need to make in the following fields:
- Invoice number
- Issued and Due date
- Service Details - Where you can write anything specifically for the appointment. For example, if the service address is not the same as the billing address of your customer (billing address is always auto-pulled and cannot be edited) you can use the wildcard {{appointment.address}} in the Service details box, and that way the alternate address gets pulled so there you can have an address where you actually delivered your service.
- Description - In this field, you should list the services you are charging, their price, and quantity. By clicking on the +Add line item you can add more services you provided.
- Message for the customer