Is it mandatory to have PAN number to apply in an IPO?

Yes, Since July 2006, SEBI made PAN number mandatory for IPO applicants. Forms submitted without PAN number or wrong PAN numbers are considered as faulty application and they are not considered for IPO allotment.

It's highly recommended that you double check your PAN number information before submitting the IPO application form. If you are filling the IPO application through online stock broker, make sure he has correct information.