I'm trying to setup a note at the bottom of all invoices to show the company banking details. It shows fine on the "customization" screen but doesn't reflect on invoices

Let's make sure that we have selected the customise template, lindria.

The changes you've made will reflect on the invoice template you've created. We can verify this by clicking Customise on the invoice form. Then, selecting the customised invoice template you've created.

If you've selected the correct template, we can perform some troubleshooting steps to determine what causes this issue.

We can start by using an incognito window. This type of window doesn't store any file history making the page to load faster. If it works fine, we can go back to your regular browser and clear its cache. A piled cache can be the reason for some unexpected issues on the pages we've opened like QuickBooks.

You can also use a different browser. There are times that the current browser we're using has a page maintenance.

Please let me know how things work on your end. 

I have tried what yousay but when I click on customize at the bottom it does not show a Banking details template.

Hi there, @Henry17.

Welcome to the Community. I can provide some clarification about creating invoices in QuickBooks Online.

The template names showing from the Customise option will depend on the information entered in the Custom form styles section. You can update the details in the system to ensure it will show what you need for your customers.

Here's how:

1. Click the Gear icon in the upper-right corner.
2. Select Custom form styles.
3. Search for the invoice template you want to use.
4. Press Edit below the Action column.
5. From the Design tab, edit the template name (ex. Banking details template). 
6. Go to the Content tab. 
7. Add a note.
8. Enter the necessary information.
9. Hit Done. 

Once done, you can proceed with creating the invoice. Please make sure to select the correct template for the banking details to reflect on your end (see screenshot below).

Also, you can view the full details by clicking the Print or Preview option at the bottom.

For additional reference, I've attached a link you can use about uploading a custom template in QuickBooks: Import custom form styles for invoices or estimates.

Drop me a comment below if you have any other questions. I'll be happy to help you some more.