Hi yil and welcome to the forum
Yes you can negotiate a revised dividend, but only if you are struggling to make the payments and there are risks for creditors if they allow the arrangement to continue in its current form.
If you are seeking to pay the IVA off, simply because your fortunes have changed - ie your property has increased in value and you feel that a re-mortgage is a good exit route, then you ought to be offering at least the dividend you originally pledged, and I always encourage my clients to offer a bit more to make the revised proposal attractive to creditors, and thus guarantee success.
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