Interest Question?

[EaglesFan2006]

Just a quick question...I have a Cap One card where the promotional no interest period is ending.  I plan on paying off the balance in full, but was just wondering what interest rate i would be looking at if i didn't?  Currently, the balance is $420.  Now, I know that they calculate interest based on a daily rate, but how far back does that go?  I usually made regular $100 payments a month while it had no interest.  My new plan is to pay it off and then use it for phone and car loan.  So, if i get with interest charges before that, will it be calculated based the regular monthly balance or will it be affected that the balance may have carried for a few months.

Also, is there a good resource or tip to negotiate lower interest rates?

[OnTheRebound]

I don't have a Cap1 CC, but if it's like any other 0% promotion, interest will be charged to your account from the purchase date if the promotional balance is not paid in full on or before the promotional period ends, which will result in a sizable interest charge if not PIF, which is what they are hoping for.

[EaglesFan2006]

So how can I figure this out?  I mean, do payments I've made in the past apply to earlier purchases?

[IOBA]

Call them up and ask them.  

Or go back to the paperwork that came with the offer.

[Wolf3]

If you have a 0% interest on purchases for so many months, then the interest with start on the first day of the statement after it runs out. 

If you have a 0% deffered interest deal (common for big single purchases on store accounts), then interest would go back to day of purchase.