Why don't you take the time to read the instructions on IRS Form 1040-ES before posting that " there shouldn't be anything quarterly to pay". And there is no place to register as a trader.
He's probably referring to notifying the Irs that he's making a mark-to-market election under irc 475(f)(1) to treat trading gains as ordinary income so that it can be reported on the schedule c. Technically its required by april 15 of the same year but when I first did it (and it only needs to be done once), I made the election in a statement at the end of my tax return following the years trading, thus a year 'late', but never had a problem with it. Its discussed in pub 550 under section 'special rules for traders of securities' iirc.
this part is the most relevant to OP I think. I am not a tax attorney and I hate taxes "Prior Year Safe Harbor The same "prior year safe harbor" you use to determine whether you have to pay estimated tax (see Who Must Pay) can be used to determine how much you have to pay. Example: Your total tax for 2001 was $37,000. Your withholding and credits for 2002 will be $21,000, so you can't rely on the prior year safe harbor to avoid paying estimated tax. But you can use the prior year safe harbor to determine how much to pay: $16,000, or $4,000 per quarter. The majority of people who pay estimated tax rely on the prior year safe harbor. It has some major advantages over actually estimating the current year's tax: It's easy. You don't have to track down a lot of numbers or do any complicated calculations if you use this method. All you need to know is the total tax from the prior year and the amount of withholding and other credits you'll have this year. No guesswork. Perhaps it's an exaggeration to say there's no guesswork in using this method, because your withholding or credits could turn out differently than you expect. But when you base your estimated tax on the prior year's tax, instead of 90% of the current year's tax, you're starting from a much firmer number. Some people wonder whether they're permitted to use the prior year safe harbor even if they know they're going to owe more tax for the current year. The answer is yes. If you qualify, the prior year safe harbor is a safe way to avoid the penalty for underpayment or estimated tax, no matter how large the underpayment is or how obvious it was that you would end up having an underpayment " http://www.fairmark.com/estimate/howmuch.htm