Every time I raise an invoice it keeps coming up with paid written across it before I have even sent to my customer. How do I stop it happening?

I'll help you fix this, @mandy28.

There may be customer credits that we're automatically applied to the invoice that why it's showing as paid. To isolate the issue, you can go to the Account and Settings, then turn off the Automatically apply credits option. Here's how:

1. Select the Gear icon.
2. Choose Account and Settings.
3. Select Advanced on the left of the screen.
4. Click the Pencil icon in the Automation section.
5. Remove the check-mark in the box next to Automatically apply credits. 
6. Click Save and select Done.

After this process, you can open the invoice you've created and unlink the customer credit by following these steps:

1. Select Sales from the sidebar menu.
2. Go to the Invoices tab.
3. Locate and click the invoice to expand the view.
4. Under the Invoice activity section, select the View payment link.
    
5. Uncheck the box to unlink the credit memo.
    
6. Hit Save and Close, then choose Yes to confirm the changes.

Once your customer pays the invoice, it's time to receive the payment.

Additionally, I've included an article that will help you track all invoices that are due on a particular date range: Report of invoices that are due on a specific day.

Please visit us afresh if you need further assistance with recording transactions in QuickBooks Online. I'm always ready to help. Have a nice day!