My boyfriend has asked me to help manage his money. We are looking into opening a new bank account where his checks will be direct deposited into the account and I'll give him a weekly allowance of sorts and would be transferring money into his solo account. Can this affect my credit or tax bracket? Will I get tagged by the IRS for suspicion of illegal activities. What are the possible ramifications of doing this?
It will not affect your tax bracket so long as he files his taxes.
It will not affect your credit negatively so long as the joint account takes out no debts. If it does take out debts, then someone would need to pay them to avoid negative credit. Ideally debts should take signatures from both of you (ask the bank).
The IRS will not automatically assume that the only reason that two people might have a joint account is illegal activities.
If he withdraws money from the account in such a way to cause an overdraft, you might be responsible for it. However, it sounds like he isn't supposed to be withdrawing money from that account. So that's a potential problem but not a guaranteed problem. Make sure that you have the power to close the account without him (so if you break up later, you can take your name off unilaterally). Realize that you might have to pay a little to close the account if he overdraws it. If possible, have the bank refuse overdrafts.
Consider a savings account rather than a checking account. The rules may better fit what you want to do. In particular, if you are limited to transfers, that's safer than checks. Schedule a time to talk to someone at the bank about the account. Ask them to leave plenty of time because you have questions. Explain what you want and let them tell you how to structure the account.
That's a sensible plan. No there's no reason for the IRS to see this arrangement as suspicious, particularly because the deposits will be from paychecks; you have a record of where all the money came from. Conversely, multiple cash deposits might be considered suspicious.
It can only affect your credit if you have credit lines associated with the account (like an overdraft line of credit).
Interest earned could increase your tax liability by a tiny amount, but in the current interest rate environment, that's not much of a worry.