Yes you can claim HRA exemption at the time of filing of your income tax return in case it is not incorporated in Form 16 subject to proof and documents as said by Mr. Rajkumar TG
whether company has allowed hra but inadvertently missed to show in form 16? If yes the you can claim hra. but if no hra is given by employer then it will be Nil and hence out of three categories where u need to select minimum of them will be Nil one and you won't get HRA. in that case u can claim rent in section 80GG