it depend on whom you are, why do they send you money, how much send to you? how often do they send?
if you are student, they send money for your tuition, living expense, etc, less than 3W yearly, it is reasonable, it would not have problem,
if you are working, and have good income, they send you some money for really gift, like a few thousand dollars once a while, it is OK, or they send you one time big money to support you to buy the house, it is ok too, but you need to declare. but if they always send you big amount of money, and you can not have good reason to explain. then it will be the problem