Re "coins are not yet available on any exchange" I think simply, income 0 and cost basis 0. People keep forgetting IRS notice 2014-21 uses term "convertible virtual currency" is taxable. Now since a coin is not listed anywhere is definitely not "convertible". (This also makes me think only cryptos with direct USD pairs are considered "convertible" so for example DGB to be not but for the sake of tracking you still need report BTC->DGB but if you wanted to use "privilege" DGB is not convertible and you go DGB-BTC then I guess and gain in BTC would be "income" but then how you "going back" to original BTC you sold for DGB) anyhow I'm 100% sure there is nothing to report for coins not listed anywhere. They are not convertible. And if ever became, you had 0 income X years ago and cost basis 0, so once sold you have 100% gain to report as taxable. (Very side note, I would do same for forked coins, cost basis 0 because there were no price at the time of fork, unless some exchange listed it before the fork but then the price is fake in a way like a "future contract" while you should report as fair market value, so logically 0, no market available until coin available)
