I have worked for the same firm for many years. I was in a iva during that time and completed it successfully.
Now many years later the firm are carrying out credit checks amongst other security checks by a third party. If that third party ask the question have you ever had a IVA and I answer truthfully can my employer terminate my employment. By the way I never at the time received any I formation from the employer to say we had to notify them.
I am afraid that the answer to your worry lies in your employment terms and conditions. There have been several instances, in the past, where forum members have been credit / security checked by employers and none have, as far as I recall, reported any problems following the exercise.
My opinions are merely that .. opinions based on experience. Always seek professional advice.
IVA Completed 23rd July 2013 .... C.C. 10th January 2014