Up to three months from the time the termination certificate is issued, which itself could be up to 6 months (usually a lot less) from when the IVA was declared a failure. It will remain on credit reference agency files for the full 6 years from the start.
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