80g exemption in itr 1

I am a government employee and during the last year, along with others, contributed to CM's relief fund. My employer deducted the amount from my salary and remitted the same along with contributions from others. While this is shown in form 16,My employer is unable to provide mandatory details like PAN etc if the relief fund without which I am unable to show this in my ITR 1. How can I then claim this 80g deduction without the mandatory information?