UC - Compliance Telephone Interview (possibly SIPP related)

I have received an email informing me that a compliance officer needs to conduct a telephone interview about my claim in two weeks. Most of the letter seems generic apart from this section:

Please call us straight away on the number at the top of this letter if you get any money from a trust or charity. Certain trusts and charitable payments are not taken into account for benefit purposes. If you get money from one of these, you may not need to attend the interview.

I started claiming UC about 2 years. A few months later I applied and got PIP. I have not mentioned PIP on my UC journal. I thought PIP does not affect my UC. Also as PIP comes from DWP I assumed they would already know.
I have received a small amount of financial assistance from a family member to help with bills. I assumed family support would be ok but I am not so sure now.
My funds have always been below £6k, so I don't know why they need to speak to me.

Lastly, I assume they only want to talk about my finances as the only documents they have asked me to have at hand are bank statements.
Do I also need to be prepared to talk about my current health situation with a Compliance Officer? I assumed a health related talk would be with a health care professional?

Thank you in advance for any feedback or advice. Johnny

Thank you for the reply BIS.

I spoke to Citizen Advice and they suggested that I have been flagged in the system for some inconsistency. It is most likely because I am getting PIP and I did not inform UC.

I was under the impression it was not necessary to inform UC of my PIP award. I assumed they would already know as they are both from DWP.

The CAB person suggested that PIP can affect the UC amount even if my saving are below £6k which might result in me owing UC money.

If I learn anything of use in the interview I will update this thread. Especially if the compliance interview is because I got PIP and did not inform UC.

I had my Compliance Interview today and wanted to give an update.

Firstly, the letter suggested the compliance issue was related to money from a trust or charity. I assumed this was PIP. Therefore before the interview I called UC and informed them I now get PIP. The UC advisor told me PIP doesn't affect UC and my compliance interview was actually about 'Undisclosed Capital Savings'. Hence the letter I was sent was very misleading.

When the compliance officer called I ask if they would tell me the compliance issue. They told me it could be various issues and they would go into that at the end of the call. The call lasted about 30 minutes. It was quite detailed and ask about my savings and accounts, rent, my living situation, etc

At the very end of the call they told me I had been flagged because a large sum of money had been reported to HMRC in 2022. I was shocked as the number was large (over 20K) and was definitely not part of my savings which are under 6K.

After the phone call, I realised it might be my pension which is in a SIPP. Apparently my SIPP provider requests basic-rate tax relief from HMRC. I think HMRC send this information to the DWP. I now wonder if my compliance issue might actually have been caused by me having a SIPP.

I assumed having a pension or SIPP would not affect my UC as I am not old enough to access any of these.

It would have been very helpful if DWP has just come out with the issue at the beginning and then I might have able to figure out where they got this number that had been reported to them.