Charging more than 50% of the limit on a card has a negative impact. But from what I see, credit score calculation takes into account the utilization ratio which is the total balance over total limit. So if the total limit is high, I don’t think charging a little bit more (for example with BT) on one card will necessarily affect credit score significantly negatively. Of course if you have only one card, that’s another story. I have obtained multiple copies of credit score in the past couple of years and some don’t show any downside of high utilization ratio. Plus, any negative impact will be short term. As soon as the high balance is paid off, the credit score bounces back immediately. So I am not too worry about the ratio.

a) Even with my A+ credit, initially, most credit card companies only approve you for up to 10k if you’re lucky. I’ve even called immediately after approval and they indicated I must wait a few months to increase the credit line.

b) When you charge more than 30% of the credit line on any credit card, your credit score will go down. Just try it. Take any card you have, and charge 75% of the entire credit limit to it. You will see your credit score go down within 1-month as soon as the credit agencies know about it. I’ve done a lot of research on this.