I am having the reception at the same place as my ceremony. Is it ok to write on the bottom of my invitation reception immediately following the ceremony or do I need a reception card????

I think it is okay that way you can save on postage

It is definitely ok to add this to the bottom of your invitation especially if the reception is at the same place.

The only time you need an additional reception card is when your information does not fit at the bottom of the invitation.