Employer Y is asking my current company I-797C receipt number

I got an offer from Company Y and they are asking my current employer I-797C receipt number for H-1B Visa transfer since my H-1B Visa will be expired in 2-weeks.

Is it safe to provide my current extension receipt number to Company Y for H-1B Visa transfer?

Please share your thoughts and experience.

It is a genuine ask for any company willing to transfer the H-1. Once you have done your homework about this new employer, it is safe to give them your receipt number.

Thanks Saurabh for reply.
But why do they need my receipt number by current employer? I have given all the documents to Company Y for H-1B transfer but they are asking for my current receipt number, i am just worrying if Company Y will do some changes on my visa case with my current employer?

In order to show that you are cap-exempt, they need proof that you have already been cap-counted before. For this they need copy of the receipt. Actually, lot of them ask for approval notice and not just receipt notice.