I like the initiative, though not sure this is the optimal approach, if using monthly averages.

To keep in mind: averages won't give accuracy.

Could end up overpaying the taxman with this. Though likely to overpay even more, considering this'd be averaging to consider 'earnings' simply as "income" - overlooking that matter of capital gains/losses.

Of course, the capital gains/losses matter is a fucking headache and a half, because how do we determine which exact Steem being withdrawn was earned when?

That question aside, I think it'd probably be possible to improve upon this design as could probably pull data from the blockchain - and possibly APIs from exchanges like Poloniex/Bittrex, if not from Steem itself - to determine the precise dollar value (in any denominated currency, pulling exchange rates from other official sources) of each precise curation & author reward at the time it was sent.

Would be more complicated to program, though I'd be happier using that as a starting point rather than attempting to use averages - even if it didn't address the capital gains/losses factor...