Stuck in a Loop

Hi, 

I created a TAX CODE and then I created a Category and linked it to the tax code.  I then put in ONE transaction.   

It didn't work to show in the BAS Report so I'm trying to UNDO this.  I removed the transaction first. BUT I cannot delete the tax category because there is a Tax Code assigned AND  I cannot delete the Tax Code because there is a Category assigned.   So i can't undo what I did. 

Please fix this loop as I cannot undo what I setup.

Regards,