We can troubleshoot the issue to determine if the browser is causing problems when creating a posting. I'll provide an article for your reference. 

Concerning your query about why exempt entries appear in VAT Payable, we can verify if your customer is tax-exempt and then determine whether the product you are selling is taxable or non-taxable in the Sales tax category.

Going back to how to delete browser cache and Intuit-specific cookies to quickly fix issues when using QuickBooks Online, open this article: Clear cache and cookies to fix issues when using QuickBooks Online. 

Moving forward, to set up tax-exempt VAT, follow these steps: 

1. Go to the Sales section and select Customers.
2. In the upper-right corner, click on Edit and scroll down.
3. Under Additional Info, check the box that says This customer is tax exempt.
4. Click on the dropdown menu for Reason for exemption.
5. Finally, click Save to apply the changes.  

Additionally, to change and check the Sales tax category from Taxable to Nontaxable, refer to this article: Add product and service items to QuickBooks Online.

We can check out this resource on how the app calculates the correct VAT rate on each sale in QBO: Learn how QuickBooks calculates VAT. 

Consider exporting your data to Microsoft Excel if you need to access it outside QuickBooks for future reference. 

Feel free to return to the Community if you have additional questions about VAT in QBO. We'll offer prompt assistance.