Form 1099-DIV reports dividends and capital gain distributions you received from stocks, mutual funds, and ETFs. Your brokerage sends it to you by January 31. Box 1a shows ordinary dividends; Box 1b shows qualified dividends (taxed at lower rates). Box 2a shows capital gain distributions from mutual funds. Report dividends on Schedule B and capital gain distributions on Schedule D. Even if you reinvest dividends, they're still taxable.