It Depends, 18+? Do you mean 19 or 20 ? That would be a John Legend 24th Anniversary 1997-2021 thank you for the memories signature shirt. Are they in college, are you still “taking care of them”? Then yes. Since you are supporting them then you have the right to know whats happening in their financial life. On the flip side, if the young adult (notice I don’t say child) regardless of whether they are 18+ or whatever, you have no need to check any account that they may have. Especially if you are not supporting them. Hopefully, you have brought up an independent, successful young adult. One that you don’t need to hover over.