first read the rules and regulations concerning the competition you are shooting.
most comps do not allow you to score your own cards. although unofficially you can, but do not use shot gauges etc. and do not write the score on the card.
usually the card's shot will have to be witnessed by a club official, and by doing so confirms that they have been shot to the rules and regs.

some organisations can be overly anal about it all (not mentioning names)
down to the point of refusing comp card shot on different brand of card!!!

read and re-read the rules, is the best advise i can give.
if posting, get proof of posting.