Alright,
You guys are making this far too complicated, something which is very very simple!!!! I have rebate traded before, and it is a very simple process.
Some of you are mixing up your vocabulary.....ECN fees, passthroughs, retail fees all mean the same thing. Rebates, negative passthroughs also mean the same thing (the opposite of the former).
WHen you bid or offer you ADD liquidity, some of you may have difficulty understanding this, but that is just the way it works. Imagine someone hit every offer up for 2 price levels. THen imagine no other offers were put in their place, and no new bids were placed either. This, technically, would decrease the liquidity of the stock by decreasing the shares in the book, and widening the spread. Dont argue this, its just how it works.
The fees for retail are more than the rebates you get for a filled bid or offer. This is how the ECNs make money.
To rebate trade you simply do this.....imagine you are trading worldcom (WCOEQ) for credits. It is .116 by .117 on Inca and ISLD. Yor default is, say 40,000 shares. You put a bid on Inca and abid on ISld at .116. You get filled on both, and have earned Inca credits of 2x40 (at 2 dollars per thousand) = 80 bucks. On ISLD you earned 1.1x40 = 44 bucks. Now you are long 80,000 shares. Offer out on both ISLD and INCA....repeat bidding process. If the bid went down to say .115x.116 then you may get out even, sometimes you can get out positive if the spread doesnt move and is filling on the offer. If you figure you got filled on ISLD and INCA in and out, then you would have earned $168 in and out on that trade. So if you took two tenths hit because you got filled onthe way down, then offered out, then you would have made only eight dollars on the trade *as each tenth with 80,000 shares is eighty dollars.
In other stocks that are more normal than this one, its harder...obviously they move a lot more. But try to at least bid or offer out after a big move so you dont pay retail both ways.