It is best to clarify with your IP as technically all the terms still apply but obviously by the end of the iva you have complied and it is unfair for you to bound to the arrangement because of administrative delays. Some firms give out letters saying that you have fully complied while you are waiting for the certificate to release you from the terms. x
If your IVA states that you will pay 60 payments, then your responsibility for uplifts from overtime/bonuses etc ceases upon the payment of the last payment.