Can you possibly hit yourself

For Example If I entered a bill a year ago or so and for some weird coincidence I got it back again, entered it again 6 months from now, will it still come up ERROR YOU HAVE ALREADY ENTERED THIS BILL ???

yes, I believe it will still give the error.

Yes it will come up like that. A friend of my family who knows I track came across a bill in the summer. He gave me the number to enter and it was one of my bills. The error message came up.