The custodian, which I assume is the grandparent in this case since you haven't been told otherwise, would be the one receiving the normal statements. You wouldn't have any grounds to challenge the change of address, since you don't control the account. Just like with any other investment account, there should be tax documents generated each year that will provide all of the information you need to file a tax return. As long as your father or the firm/bank provides those documents to you, there shouldn't be any issues with the tax returns. Beyond that, I wouldn't worry over where the statements go, unless you think he's trying to shelter his own money from taxation with no intent of actually gifting it.(That's another legal matter, with serious tax repercussions for him, not you)