I am doing large amount of transaction, including coin-fiat and coin-coin and found doing transaction based tax calculation is impractical. I came up with the following simplified method, and would like to see whether it's acceptable.  I am expecting answers from professionals, so please let me know if you are a CPA.

suppose starting with nothing, I spent $B amount in buying different types of coins, and received $S amount in selling coins, I paid $F in fee and finally i have $M worth of coins, based current market value.
so my capital gain is $M + $S - $B - $F, and all my coins will have current market value as its cost base. i would ignore all the coin-to-coin transactions, and fees paid using coins. 

If the above method is acceptable, then it's a much easier calculation.   
The main downside is that i am treating the $M as realized gain, which is fine if the coin value goes up, since it increase its cost base. all the transactions are done this year, so i am not worried about long term vs short term.  if you have a more tax efficient and simpler method, please let me know.

Many thanks!

I am using a major us based exchange and managed to pass the higher verification level (by providing all kinds of private information, such as credit history, income source, id, employment, etc ... )  and was granted to deposit and withdraw up to $1 million a day.  After putting in a large amount of USD, i was told "due to compliance change", they now only allow $100,000 dollar withdrawal a year!  though i could still convert USD into crypto currency and withdraw to another exchange and sell, it causes a loss. they also refused to give any details on the 'compliance change" and didn't explain why there was no notice. I was wondering whether such act,  lowering the withdraw limit significantly on fully verified clients without notice, is legal and is there any action i can take. thank you!

I put my gdax public wallet address in  blockchain.info and did a search.  i found the address but the balance is very different from my balances shown by gdax (which is correct).  i tried search for my other wallets in other exchanges and got the same results. I wonder how is that possible.