Hi there and welcome to the forum
I do not agree with your IP's stance here. They should be reviewing your overall salary at the end of each year, and using that new figure as the basis for future 50% uplift payments. An IP who does not take account of a debtor's increased expenditure, is setting themselves up for a disgruntled client, struggling and missed payments and potential failure. That is certainly not acting in the best interests of creditors.
Be more firm in putting your point across. Can I ask who your IP is and which firm?
Regards, Melanie Giles, Insolvency Practitioner for over 20 years.
For further details contact me at
http://www.melaniegiles.com and view my IVA blog at:
http://melaniegiles.blogs.iva.co.uk