ok i think i found a lot of issues here.
according to the guide here, Manager will not create the Tax payable account by default for new businesses, yet it still does.
when you create a new tax code Manager sets a greyed out Tax payable account by default.
this creates an uncategorized account in the COA.
i renamed the account to the exact same name Tax payable and added it to the Liabilities group.
the said amount still remained in Suspense.
when i edit the tax code, the account is still greyed out.
but when i try to change the account to the renamed account it shows as below.
i deleted the relevant tax transaction and the tax code. this automatically deleted the renamed Tax payable account. this proves the account was created by default when creating the tax code.
now i created a new Tax payable account under Liablities and then created the same tax code and set it to the correct account. then created a payment to the Tax payable account and now everything shows correctly in the summary.
@lubos i think the issue here is that Manager still creates a default Tax payable account when creating Tax Codes.