Requirements vary from firm to firm and, sometimes, from review to review --- usually last three payslips and/or P60, along with supporting evidence if you are increasing expenditure by any great amount. But it is best to ask FJ direct, or, maybe their on forum rep will pick this up and respond.
My opinions are merely that .. opinions based on experience. Always seek professional advice.
IVA Completed 23rd July 2013 .... C.C. 10th January 2014 http://foggy.blogs.iva.co.uk
Foggy is quite correct, the most important thing is for your payslips / P60 or other proofs of income to be up to date. This is so we can check that you are still earning your allowed income, and to ensure that additional monies aren't building up on your IVA. Its best to deal with these as they arise, rather than at the end of your IVA.
If there have been any major changes to your expenditure or circumstances then we need to know about those too, and we will ask you to evidence those changes.
If you'd like the team to talk you through the process drop me an email to ian.williams at FreemanJones.com and we'll give you a buzz.