@79b79aa8 Again, I'm not a tax authority and this isn't tax advice, but I could see the ledger being treated as one undifferentiated whole. If you sold your BTG (for fiat) at a time when it constituted 2% of the ledger, you sold 2% of your bitcoin ledger claim. If you then flipped your BTC entirely into BCH, nothing happened. If you flipped back when BTC was on a dip, then flipped back again to BCH when BTC did its final deadcat bounce and ended up with much more of the Bitcoin ledger than you started with - good for you. I would still want to say that that is just the ledger stake you bought in 2013.
In that way, Bitcoin would be a kind of asset you can grow if you play your cards right. Like stock in a company you run. You can increase the value of your shares by doing a good job, and in the process your shares may split, but no new assets have really been created.
Trading among them might be considered a like-kind trade, but I don't really know. Seems fairly simple to do accounting for, though, and if I were the IRS I'd care foremost about if there is any way to cheat the system. I don't see one here.
In fact, doing the opposite - that is, treating a spinoff as an asset you purchased on the spinoff date - seems to lead to oddities. If the spinoff dies, is that now a tax writeoff? If you buy a stock and it goes to zero, that loss is normally allowed to cancel out some of your taxable capital gains, right? If anything, treating a spinoff as a purchase seems to open the door to cheating. This seems to reinforce the idea that it should be treated like a stock split.
One additional major problem with the "trades between spinoffs are taxable" theory is that most exchanges don't even have BCH-fiat trading pairs yet. If they still don't have them by August, it will have been impossible for many people to sell their BCH for fiat as a long-term gain even after a year has passed, because they'll have to go through BTC first. And if, say, the ratio hasn't changed there is no gain on the long term (no tax incurred there?), and all the tax will be incurred on the short-term BTC holding? Seems quite unfair. (Though this seems to apply to every cryptocurrency without a direct fiat trading pair.)
The simplest analogy would be that of a casino as if all the cryptocoins are one big casino: you go in and buy $1000 worth of tokens and gamble them (by trading them around with other tokens, or just by holding the tokens). If you end up with $1500 worth of tokens after a year and then redeem the tokens with the house, is that not just $500 of long-term capital gains?