Didn`t realize the SEC constantly changes their "securities transaction fee" aka SEC Section 31. My understanding was it was a constant fixed rate, seems not.
So the previously stated -0.0000192 * Notional Value is no longer correct and its now
$22.40 / 1e6 -> -0.00002240 * Notional Value
There`s a nice history of the rate here.
Not sure why it constantly changes, so lets dig into the docs. Presumably SEC needs hit a specified $$$ value each quarter and if the volumes drop enough they need to bump the fee,
... and thats pretty much what happens
"Specifically, the Commission must now adjust the fee rates to a uniform adjusted rate that is reasonably likely to produce aggregate fee collections (including assessments on security futures transactions) equal to the regular appropriation to the Commission for the applicable fiscal year."
Whats interesting is the number for "regular appropriation to the Commission" which is.... $1,321,000,000
So the SEC`s revenue from this tax alone is $1.3Bn wow! But is pretty small when compared to the aggregate Personal & Corporate tax revenue each year.