Some appear within weeks, others it takes a few months --- it took me over 6 months to appear on the Register ! Online CRA reports (Clearscore, Noddle, etc) can be up to two months behind the times and will usually report the IVA a few weeks after it appears in the Register.
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