Problem with Tier 4 right to work check

Hello,

Please I have an issue with my recent Tier 4 right to work check that was conducted by my employer.

Basically, my employer employed me with my Tier 4 visa after completing my PhD and I have since switch to Tier 2 general under their sponsorship. However, I recently got to understand that the right to work check that was conducted on my Tier 4 visa was not correct.

My employer used the old list A and B and not the new list on published in 2014. Based on this, my valid Tier 4 visa was on an expired passport and the employer took a copy of the valid visa and the new passport I have. I understand this is wrong and that since my valid visa was on an expired passport, they should have asked me to do a TOC. Although I have changed the visa and I am now on an Tier 2 visa, I am worried that this might be discovered if we are audited by the UKVI compliance team.

Now here is my question.

Should I tell me employer of this mistake and bring their attention to the new requirements, which I believe they are not aware of till date? If I do will they not simply fire me to keep their record clean? If I don't and it gets picked up in a compliance audit, my employer may loose their licence and that will also affect me.

Please any one have any suggestion?