Some, or all, of your investments can generate income and/or capital gains from time to time. This would be the case if, for example, you receive dividends on stocks that you own, interest on a bond held in your investment portfolio or if you sell an investment at a higher price than you originally bought it.
These monies may be subject to tax depending on your personal circumstances and applicable tax rules. To this end, it is your responsibility to understand how these transactions impact you and your financial situation and whether any tax may be due.