post a level uni application

can I only put grades from re-sit when filling my UCAS application after completing A levels. will they know that I have re-sat my A levels.

They won't from your input alone, but they can find out if they choose to contact the examining body for some reason. If you resat and got a lower grade, don't put that on as it doesn't count. If you resat and got a higher grade, put that one on.

You put the grades before you resat as well as the grades you got from the resit if they are higher than previously

Thanks for the reply, does that mean if you did worse in the first sitting compared to the re sit , you don't have to put that in your ucas form? or do you have to put both of them

what if you re-sat them twice

You do the same
First attempt as well as any resits you got a higher grade in the second time, and then any resits you got a higher grade in the third time