I have entered supplier invoices for our VAT period Sept - Nov 2019 for a MTD Vat return. Quick books automatically sets dates for the next period can this be overidden?

It's my pleasure to have you here, @frasershorey,

If you're referring to the VAT End Date, you can change this when preparing a return for a certain period. Here's how:

1. Go to the Taxes menu from the left toolbar.
2. On the VAT page, select Prepare return.
   
3. Update the End date at the top before submitting the return.
   

Moving forward, update the VAT year to match the start of your financial year to ensure QuickBooks calculates your VAT quarters correctly. This will then calculate your VAT Filing Quarters in line with your Financial Quarters for you.

Follow the steps below:

1. Go to the Taxes menu from the navigation panel.
2. On the VAT tab, click on the Edit VAT button.
3. Select Edit setting from the list.
4. Choose the beginning month of your current VAT period.
5. Pick the appropriate date under Effective date for new scheme.

To know more about the VAT feature in QuickBooks Online, check out these articles:

VAT: Getting Started

Set up and edit VAT settings, VAT codes and VAT rates

Let me know if you need further assistance with VAT tracking, please know that I'm just a post away to help you. Have a nice week ahead!