you need to report the realized gain/loss on schedule D
EVERY YEAR. In your case, the gain seems is "short capital gain"...



Every year financial institutions will send out 1099. There are several types
of 1099. The interest amount shows on 1099-INT, 1099-DIV shows dividends and
capital gain distributions (and foreign tax paid <--- usually happens when
you have EAFE mutual funds and ETFs) , 1099-Misc shows other activities which
gets complicated..



But you must have  1099-B when you receive the proceeds from the broker transactions.
Usually it only includes the 'gross proceeds".. It is your own responsibility
to record the adjusted cost basis (original purchase price, the purchase
commission you paid, the dividend reinvest which will increase the basis if it
is a MF or ETF etc) ,  so that you can report the realized gain/loss
properly.