Usually, they report on the statement drop date --the date that it posts, which is usually around 2 1/2 weeks before the due date. HSBC reports at the end of the month, and others have completely different times.
Do you have access to any credit reports that show the actual date that each account is updated? I use TrueCredit, which shows mm/dd/yyyy on EX and TU, but not on EQ. You might do a free trial offer, if they have one going on. You don't need to look for an entire month, unless you have brand new reports. Any of the pulls will show whatever the most recent activity is, so that will cover the last 31 days or so.
Anyway, once you know the date, pay online 4-5 days before it's due to report, and then keep checking to make sure no other charges pop up. Once it has posted, you can PIF it and start all over again. Remember that on most cards, the statement date rambles around a bit each month.
You can use your card as much as you like (or they'll let you) and pay your account down multiple times a month, as long as you have the timing down. As many cards as you have, you might even keep all but 2 or 3 cards PIF'd, and just let those report. Air each card out every 6 months or so to keep the CCC happy.
I just got a nice score jump on TU doing this. Good luck!
* Credit is a wonderful servant, but a terrible master. * Who's the boss --you or your credit?
FICO's: EQ 781 - TU 793 - EX 779 (from PSECU) - Done credit hunting; having fun with credit gardening. - EQ 590 on 5/14/2007