Persons who have the right to receive dividends are taxable on dividends. Whether the buyer or seller includes a dividend in gross income depends on when the sale took place, if the dividend is paid after stock is sold.
Persons who have the present enforceable right to receive dividends are taxable on them. If an agent or nominee receives the distribution, s/he is the non-controlling record owner of the underlying stock[i].
[i] Freuler, John, admr v. Helvering, (1934, S Ct) 13 AFTR 834, 291 US 35, 78 LEd 634, 4 USTC P 1213; Champion Trophy Mfg Corp, (1972) TC Memo 1972-250, PH TCM P 72250, 31 CCH TCM 1236; Nicholls, North, Buse Co, (1971) 56 TC 1225, acq.