ILR SET (M) - how to obtain application reference number?

[Gardyvol]

Hi all, just have a quick question and would be much appreciative of any help. If this has been asked before, I also would be much appreciative if you could point me to the right thread.

Applying for ILR on a SET (M) 5 year route.

Home Office received my application by post on March 6 and took payment on March 7. My visa expires on March 19, so how do I obtain the reference number of my on-going application so that my employer can verify that my work status is valid after that March 19 expiry date until a decision has been made on my application?

Again, any help would be appreciated.

Thanks
Yank in Scotland