@iJoel wrote:
-It has a very large credit limit to help my revolving util.
There are two ways to lower your util: 1) increase your reported credit limits and/or 2) lower your monthly reported balances. $1 / $100 = 1% is just like $100 / $10,000 = 1%. There is no difference whatsoever from a util point of view.
A bit about rainy days. If you are AU on your mother's card, and she needs to charge more for a while, your util will increase. If you're not AU and you pay down most of your monthly balances before the statement date, your own increase in charges/util would apply as well.
One question is which of the two of you would be least likely to be affected by a rainy day. Another question is how you feel about AU status in itself. It's about young vs older, about independence and that sort of stuff. 
@iJoel wrote:This specific card card does report balances.
-It's younger than my average age of accounts.
-It is squeaky clean.
-It has a very large credit limit to help my revolving util.
-When she starts using her other card instead of this one, it'll post ~1% every month.
-It does report to the Credit Bureaus.
And yeah, I'm guessing the reported balance is just pulled randomly each month. So if I can get her to use another card, I can only imagine it would help my credit, seeing as it has such a high credit limit.
No, there's nothing random, except for the occasional and uncommon instances where lenders update twice in a month.
With a few exceptions, CC's report the balance that's on the statement that month. This is the balance that posts, that the consumer then turns around and pays before the due date. So it's not the balance left after payment; it's whatever is showing as due when the statement generates. For instance, someone can have an $1800 balance report on a $2K CL card, and they get killed by 90% util, even though they promptly pay it off every month.
Here are some of the exceptions to they-report-the-statement-balance: HSBC/ Orchard bank cards (not store-only cards) and USBank cards update the balance that shows on the last business day of each month, regardless of what the balance was on the statement, or what the balance was after payment.
As I mentioned above, this is one of the tricky things about being an AU. (I was one on my former husband's card, for the length of history.) We really can't demand that they not use the card, or that they pay early, or that they not suddenly buy a houseful of furniture and carry a huge balance for a year. So as PP said, you're vulnerable. In fact, my AU card is still reporting to all three of the CRA's, even though I came off of it in January. It wasn't updating, or so I thought, but a balance posted this past month on my Experian report, and there it is, looking as current as ever. He was pretty good-natured about my asking him to pay his balances early when we were married, but it hardly seems right that I do this now. 
(Even though we have a very cordial divorce.) So I've got this potential loose cannon on my reports, in the form of a card that I'm not even an AU on.
If you can use an AU card to help get more credit in your own name, which it sounds like you're trying to do, that makes sense. You can come off the card when you no longer need it, and you won't have to worry about surprises popping up.
Okay, so thanks to everyone's help. I decided to contact all of those credit agencies & have me removed (after removing myself as an authorized user). Transunion removed me within a day, but the other's are taking longer. So now my total credit limit is $2200, and I'm going to be putting around $1000 on cards. Which I figured was bad, but I just realized. Couldn't I pay them off before the 'term' ends and thus have 0% utilization on my credit report? Granted I would want more than that. I'm thinking like 15% utilization is ideal? What do you guys think? Is that even possible? And if so, what would be a good percentage to 'show' them?
Thanks for all your help .
@iJoel wrote:Okay, so thanks to everyone's help. I decided to contact all of those credit agencies & have me removed (after removing myself as an authorized user). Transunion removed me within a day, but the other's are taking longer. So now my total credit limit is $2200, and I'm going to be putting around $1000 on cards. Which I figured was bad, but I just realized. Couldn't I pay them off before the 'term' ends and thus have 0% utilization on my credit report? Granted I would want more than that. I'm thinking like 15% utilization is ideal? What do you guys think? Is that even possible? And if so, what would be a good percentage to 'show' them?
Thanks for all your help
Sure, this is called playing the util game.
Do you have any CC's from US Bank, or bank CC's from HSBC/ Orchard? If so, they have a different way of choosing which balance to report, so read below.
Otherwise, almost all CC's report the balance that shows up on your statements. Go online 4-5 days before the next statement is expected (some are on the same day of the month every month, others vary a few days in either direction) and pay them down to whatever figure you prefer. Check back on the morning that the statement drops to see if anything has popped up at the last moment and pay it too. Most CC's will credit the payment before the statement cuts; this might be required by the new Credit Card ACT, I'm not sure.
For US Bank cards and HSBC/ Orchard bank cards (not store cards like the HSBC Best Buy store-only card), your balance as of the last business day of the month is reported. (I recently read a post that said last Friday of the month for HSBC/ Orchard, so be aware of that possibility.) Do the same deal of going in 4-5 days earlier and paying to whatever balance you want to report.
Ideally, you won't have all your cards reporting balances. Also, most people's scores are hurt if all report $0. 
If you really want to torture your reports for ideal scores, let all but one report $0, and let that one report $10 - $20, as long as that's 9% (not 15%) or less of that card's CL. Then be sure to go back and pay off that remnant. (This is really easy to forget to do. )
Util is the one thing that the consumer can directly control (as long as you have the money to pay your debts, of course), and it can be turned around in one cycle of all your credit cards, if they update promptly. It's pretty empowering to do this, and as an added bonus, it adds a little insulation against late payments. You've moved your personal due date up from the CCC's due date to several days before the reporting date.
It will take a while for the credit bureaus to post the new balances, but otherwise, this will do the trick.
Question: Would it be smart or helpful (or dumb and counterproductive) for you to apply for a medium-sized limit card in your own name first? I'm just wondering about the hit your UTIL might take. I definitely defer to wiser heads here.
Starting Score: 550
My wife is the opposite. She made me an AU about two months ago, and it is just starting to show up now on my credit reports. Her credit line is 31k but her usage bounces between 2k and 6k a month. This is a 3 year old card that has been paid off every single month. It is a mileage (American Airlines) card, so she charges EVERYTHING on it, which is fine, because we get at least 2 round trip flights a year from the points.
Is this correct? The 31k credit limit from her card is added to the denominator (bottom number of the fraction) of my utilization calculation and total credit used on that card is added to the numerator (top number of the fraction) of my utilization calculation. I get the benefit of her huge credit limit provided that her utilization of that card is somewhere between zero and 10%???
For example. Lets say I have 20k in credit, and her card (which I am now an authorized user) has a limit of 31k. Does that mean that my total credit available (the denominator) is now = 51k? Because I would have expected my credit utilization score to go way down due to her high available credit but low usage (it's always less than 20%), but that does not seem to be the case. And maybe this is because I have only now (within the last month) started to see her card show up on my account listing. It almost seems as if the only way being an authorized user affects you is if the card negatively affects your credit. If it positively affects your credit, than the scoring models throw the AU card out....
Starting Score at June 2010: 679