I doubt we owe them that amount ... they may not be stupid, but they definitely are DISORGANISED AND INEFFICIENT if they give tax clearance and 3 years later they discover they are being owned.
Oh and by the way they are most definitely unfair!! We have had instances where they made mistakes and then chalk it up to human error ......... yet the taxpayer is not allowed to commit human error. Ridiculously unfair.
did they refund you after discovering the error?