There are no signs! He has to be afraid of his sin until he meets Allah!

My question is … if some Muslim does shirk verbally, unintentionally or intentionally and later he feels that he has done something really very wrong and he fully regrets over it and asks for forgiveness and he is full of shame and he repents sincerely. Then what are the signs that he is forgiven. .. as Allah forgives all sins on (sincere) repentance..Allah gave him chance to repent over this major sin.