Hi que and welcome to the forum
A very big one, as he/she is responsible to your creditors to ensure that you comply with the terms of the IVA you agreed to, and that you make your payments in accordance with the proposal.
Having said all of that, they owe you a very big duty of care to look after your money safely, and pay it out to your creditors at regular intervals. They also ought to support you at all stages of the process, and be readily accessible for you to talk to at any time if you run into difficulties.
Regards, Melanie Giles, Insolvency Practitioner for over 20 years.
View my IVA blog at:
http://melaniegiles.blogs.iva.co.uk