Hi all,
very strange situation here. Normally, when one would record a VAT payment (tax payment) you use payments - new payment - under account select ‘tax payable’
At the moment, my tax payable account is missing in the drop down menu in the payments module.
What edition, version, and operating system are you using? The built-in Tax payable account is just a placeholder. You need to define your own tax liability account.
22.1.28
OS: Mac
Edition: offline, free
How do I define the tax payable account? Also, I see that amounts have been booked under the tax payable account already (VAT)
Thank you for your quick response - very much appreciated 
Just create a Tax Payable account in your chart of accounts, and update your tax codes to refer to this account
See Create and use tax codes | Manager, especially the note about older versions and the functionality of the Tax payable account. Depending on your version history, you might or might not have a functional tax liability account named Tax payalbe. But that is impossible for us to tell.
The developer has been encouraged to remove the default Tax payable account. For technical reasons, he has declined to do so. But its presence causes confusion. And I think the relevant Guide is vague because different users have different version histories. So the program can behave differently.
You solved it