ESA Support Group but ESA 3 form arrived

My wife has been on contribution based ESA since 2011.
She has always been in the support group and she was re-awarded the benefit this year in July. She was also advised that she wouldn't be assessed again (perhaps because she is 60) unless there was a change in her health.
Today, she has received an ESA 3 ibr form and she is somewhat perplexed and anxious as to why.
The form suggests that she may also be entitled to income related ESA and asks that we provide financial details going back to July 2011.
I myself retired and had a pension lump sum at the end of 2010 which was more than £16000. I dont believe that has any bearing on CB ESA?
What is the reason for this form ?
Has anybody else had one?

Thanks

Mark

Hi
I to received a ESA3 form today. The from dated 2013 when i changed over to ESA from IB.
I am filling it in and will update you all on here if i hear anything back from them.
I will keep a copy of the form and I will be posting it back recorded delivery.

Hi
I have also received the ESA3 form to complete. I receive ESA and my form dates back to October 2012
I also have unsuccessfully migrated from DLA to PIP, all my mobility component has been taken away having received the higher rate for years. I am now going to the Appeal with it.
My question is, i 'm not sure whether it is worth me filling the ESA3 form out? My Husband has been self employed for years. However due to ill health, he was unable to work at all Aug. 2012 until March 2013. Also, from September 2015 to January 2016. Being self employed, he also has has several periods over the years when he hasn't had any work at all.
There doesn't seem to be anywhere on the form that i can put these periods down or explain the circumstances. i've had a look at the B16 and again, there doesn't seem anywhere for that either? As all in all, the times he hasn't worked have amounted to about 14 months, is it worth me filling out the form?
thanking you in advance
Mel