A downside of using DRIPs is that the investor must keep track of cost basis for many small purchases of stock, and maintain records of these purchases in paper or electronic form. This assures that the investor can accurately calculate the capital gains tax when any shares are sold, and document cost basis to their government if requested. This record keeping can become burdensome (or costly, if done by an accountant) if the investor participates in more than one DRIP for many years. For example, participating in 15 DRIPs for ten years, with all of the stocks paying quarterly dividends, would result in at least 615 share lots to keep track of—the 15 initial purchases, plus 600 reinvested dividends. Further complications arise if the investor periodically buys or sells shares, or if the company is involved in an event requiring adjustments to cost basis, such as a spin-off or a merger.