Do all of my creditors have to agree upon the monthly payments
No. In fact only 75% of your creditors need to accept the agreement. And
, since it is a legally binding contract, they can't change their minds and stop the IVA once it has started. You IP will aim to design a plan that will suit the vast majority of your creditors, sticking to the idea of creating reduced payments for you. The reason your creditors are likely to accept an IVA is simple: it is a compromise in order to get the best return on the loan they gave.
Do all of my creditors have to agree upon the monthly payments