I submitted my FAFSA earlier in January and the deadline for UC’s is March 2nd, however I made a huge mistake and I only realized it TODAY. I did not add UCRiverside at all. I panicked and added it today and I am now wondering if I will still be eligible for grants and financial aid package and will my financial aid be reduced. Will I need to pay out of pocket?
let them know
At least you put one UC so your cal grant, if any, would be available
http://admission.universityofcalifornia.edu/paying-for-uc/files/fafsa-tips.pdf
As @BrownParent noted, so long as any UC is listed, you’ll be eligible for a Cal Grant - it’ll be transferred to whatever school you decide to attend.
What could be affected, however, are any additional grants you may have been eligible for directly from the university itself. It may or may not make a difference - I just don’t know. That’s why you should contact UCR as so as possible to let them know.
And please get back to use and let us know what they say - thanks!
Contacted them today, and they told me they go by the date of my submission! What a relief, thanks for all the feedback guys 
Thanks for letting us know!