CCC #1750 - 1756 covers the morality of human acts.
Example if an individual deliberately lied to someone, they know they did lie - there is no doubt. Their
intention was to deceive the other, to mislead them, to conceal the truth to them. So what they said was a lie.
Example if an individual told another that they paid $XX for the pair of shoes, with the
intention of telling the other the truth, but later realized that they
misspoke, made an
error and in fact only paid $xx for the shoes - there was no lie as there wasn’t the
intention to lie to deceive/mislead the other. So even though what they said wasn’t strictly true at the time of speaking they believed it was true and were being honest with the other. So in this example there is no sin, so nothing to confess.
We can’t sin by accident. All sins committed are deliberate.