I have no option to send invites on iPhone 5 iCal.......

....I currently use gmail but when I create an event on my iPhone 5 it doesn't give me the option to invite anyone.

I've heard there has been glitches when restoring your previously backed up info from an iPhone4 but I have upgraded to 6.1 which I thought may eradicate these issues.

Advice appreciated.

Many thanks in advance.