Need to include standard note "VAT on this supply to be accounted for by the principal contractor" on all invoices to principal contractors. How best to standardise this?

Hi there, jhogan4.

Are you trying to add notes on the invoice template? If so, you can customize your invoice by adding a footer text. 

Let me show you how:

1. Click on the Gear icon at the top, then Custom Form Styles.
2. Choose New style or choose the type of transaction you want to customize.
3. Click on Content.
4. Click the boxes under Invoices and other sales forms or Add payment details and footer to enter any information.
5. Save changes.

Additionally, I've included an article that'll help you design your custom form styles for your invoices or estimates, then import them in QuickBooks Online: Import Custom Form Styles.

If you're referring to something else, please don't hesitate to leave a comment below. I'm always here to help you out.