Immigrationboards.com

Hi, could someone help me pls.
I'm a bit confused about the first question on the
Form AN. It says to state a UKBA or IND reference
Number. Which reference number are thy referring to? A bit
Confused abt this.

Ive also asked this question here when I was applying for naturalisation. One of the users on this board advised me to leave those fields blank, it worked out just okey.

Ok thanks