Does anyone know why Quickbooks should suddenly start asking me to enter the VAT rate when posting payments through the bank rec? Any idea how to resolve this?

I can see how the benefit of being able to post payments through the bank without entering the VAT info would aid you in managing your transactions with QuickBooks Online (QBO), @dave206. That's why I'm here to share a few details about this.

You'll be asked to enter the VAT info when posting payments through the bank in QBO to easily track taxable and non-taxable items and make sure your tax report is accurate. When the client isn't VAT registered, you can select the No VAT option and then Add the payment to your account register. Please see the screenshot below for your reference. 

We take customer suggestions as opportunities to improve the various features within our products. Therefore, I would encourage you to send suggestions or product recommendations.

Your valuable feedback will be forwarded and reviewed by our Product Development team to help improve your experience while using the program. Here's how:

1. Go to the Gear icon.
2. Select Feedback.
3. Type in your recommendation in the Share your feedback field.
4. Click Next.
5. Follow the on-screen instructions to complete the process.

I've attached screenshots below that show the first four steps. 

Also, to further guide you in managing taxes in QBO, I'd recommend checking out this article: Taxes Help Articles for QuickBooks Online. It includes topics about VAT, tax reports, and MTD, to name a few.

On top of that, I'd also recommend visiting this page to keep you updated with the latest software improvements and enhancements with QBO: Customer Feedback for QuickBooks Online.

I'm all ears if you have other VAT concerns or questions about managing payments in QBO. You can drop a comment below, and I'll gladly help. Take care, and I wish you continued success, @dave206.