<prompt> Human: Dad sent over 18k in stocks over to me that he had purchased for 15k. Its now up to 20k in value. If I sold it, what would I be responsible for paying? The 2k or would I be responsible for the whole 5k?  <response>: The gain, if you sold at 20k, would be the difference between the 15k that was paid for the stocks and the 20k that they sold for.So, the gain would be 5k.As the stocks have probably been held for more than a year, the relevant tax would be long term capital gains tax. This would most likely be at a rate of 15 though rates of 0 or 20 are possible, depending on your tax bracket.A 15 tax on a gain of 5k would be a tax of 750.Good luck. 