Disability premiums EDP and SDP back date/back pay

Hello,

I am looking for some help/advice on what to write in my ESA3 form.

A bit of background info: I was transferred from incapacity benefit to ESA (contribution based) support group in 2012. I recently found out I could put in a claim for income related ESA and then receive the disability premiums (EDP and SDP/enhanced disability premium and severe disability premium). I have been doing a lot of searching lately and I have seen that others have been successful in getting the premiums back dated to the date they were transferred from incapacity benefit to ESA, some went back quite a few years like myself.

I have been filling out the ESA3 form and hope to post it back by the end of the week. The form is almost complete but I haven't yet written in the form about the "back pay". I am not sure how to explain that I would like the EDP and SDP back dated to when I transferred in 2012. I have seen others were told there is a maximum time limit they can back date payments, max is 13 months? and I have seen others were able to get the money back dated for quite a few years.
Can anyone on the forum help me with this? If anyone could advise me on how to ask them about the premiums being back dated I would be extremely grateful.

I am not sure if this will help or not but thought I would post it just in case it does. I am on ESA contribution based in the support group since 2012. I am also in receipt of DLA middle rate care and low rate mobility. I live with a relative and they are in receipt of PIP which I believe then entitles me to claim the SDP Severe disability premium because they are on a qualifying benefit (PIP), but their PIP wasn't awarded until 2013. No one receives carers allowance for me.