I just started my personal bookkeeping. Aaand It is a nightmare.

I've tried a few methods to get a good working excel based off GDAX and Coinbase reports (different sheets for each coin, different sheets for each exchange, etc.) however I've found that the transfers back and forth between GDAX and CB alone (in addition to the other various ins and outs to other exchanges, payments for goods/services, etc.) are where I run into bottlenecks.. The key, of which I've found most logical, is to keep a running cost basis of your "inventory" and I've even found it easier to just maintain one master sheet with all activity from the various sources and coins presented chronologically.

Anyways, what I've found most useful is coding out all Rows with Buys/ transfers in to automatically calculate the cost basis remaining to be allocated amongst the proceeding sells/transfers out on a first in first out basis, but have yet not figured out how to automatically/accurately allocate them so for now my process is manual now....but I am determined :). If anyone has similar issues let me know and we can brainstorm ways to expedite this.

Also would like to note that I've reconciled about the first 50-60% of my activity and am inclined to conclude that Coinbase's gain/loss calculations per their prototype "cost basis tax report" report is not 100% accurate.