Can H1B Start date be postponed after approval date?

My question is, I have an H1B approval notice with a start date as OCT 1st, 2019. But, I still have valid STEM OPT till DEC 15th, 2019. The company I work for now and will be working for on H1B is the same. I want to use all my OPT STEM timeline and then start H1B from DEC 16th, 2019. Am I allowed to do it?. Thanks in advance.

Well, if you have applied as Change of Status, then there is no option, it will be automatic and will kick-in on October 1st. But, if your petition was filed as consular processing, then you have that option to continue on OPT and then exit country, get stamping and re-enter during end of your OPT or file for Change of Status at that timeā€¦