Answer: -There are three major credit scoring organizations. Each one uses slightly different formulas to rate various aspects of your credit profile. ie; debt to income, debt to credit line, on time payment history, length of credit history, average age of credit lines, etc. In addition each organization can put a different weight on each of these aspects of your credit profile. So with the exact same credit information, the three credit rating agencies can come up with a different but usually similar score. BUT ( and this is a big but) not all of your credit grantors may report to all three credit rating agencies. So one good (or bad) credit action may be on only one or two of the three credit rating agencies. That difference (especially when it is a bad report to one rating agency) can cause a major difference between credit scores.REMEMBER, not all information on your credit report may be accurate. Some surveys have turned up data errors of one kind or another in as many as 25 percent of credit reports. So you may have INACCURATE NEGATIVE (meaning bad) data in ONE of your credit reports. That too can cause a difference between your scores. Credit reporting agencies are obligated by law to remove any data that an individual contests if, within a given time (usually 30 days ) the Credit Reporting Agency can not confirm the data is correct.A great deal more information is available on the Fair Credit Reporting Act page, or the section titled something like " Your Rights"on your credit reports. Check that out. That would be your best guide.Keep you existing credit lines paid on time. Keep you existing credit lines active so that they increase the average age of your credit history. Keep your debt to income ratio and debt to credit line ratio low. Avoid establishing new credit lines unless absolutely necessary. Those things will help gradually increase your credit score. -Each of the 3 reporting agencies has a different calculation they use, and a different spread. If one score seems low, check the report, and you don't have to pay for it. If you've been denied credit for any reason, you can get a free copy from the bureau the creditor used to make the determination. Also, I believe there was a law passed recently that allows each individual one free report each year.