Does it make any sense that the same vendor bill is showing up in two different period vat returns?

Let's solve your issue so you can file your VAT returns accurately to the correct agency, Omega888.

Based on your statement, I take it that you've already completely paid your prior liabilities, including the Amazon bill you mentioned. If so, it will surely not show up in your upcoming VAT returns. Sometimes, local internet cache files stored in the system can cause unexpected behavior in the product. This can be the reason why the paid VAT return re-appears on your current return. 

To get rid of this problem, we can start by accessing your account in a private window. The private window will not save any history, making it a good place to identify browser problems. You can access this by pressing the following keys:

• Google Chrome: press Ctrl + Shift + N 
• Mozilla Firefox: press Ctrl + Shift + P
• Safari: press Command + Shift + N

Once you're in incognito mode, review your VAT returns. If everything shows fine using a private window, go back to your regular browser and clear its cache. Clearing the cache or cookies is the best way to get a clean slate for your browser. Otherwise, using other supported browsers can be a good alternative too.

You can also run the sales tax liability report to help make sure that everything is accurate before you file your return to your tax agency.

Furthermore, feel free to check out this article as your reference to guide you in filing your sales tax return and recording your VAT payments: 

• File your sales tax return and record sales tax payments in QuickBooks Online
• Manage sales tax payments in QuickBooks Online

Don't hesitate to reply anytime if you still have questions or concerns about filing your VAT returns. I'll be here ready to assist you. Have a good one!