Recent changes to FHA credit scoring requirements highlighted some of the limitations of credit scoring in underwriting decisions. The problem is that you don't get a good credit score by simply paying your bills on time. You must have the right kinds of accounts and you must have them for a number of years. So folks who are underserved by financial institutions, like younger people or immigrants, have a much harder time getting an FHA mortgage than they did in the past, even if they never missed a payment in their lives.

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It takes using a variety of credit for years to earn a really good credit score.

Take a look at myfico.com's little pie chart. Your payment history is 35 percent of your score. That leaves 65 percent attributed to things like length of history, the types of credit used, utilization (amount owed versus amount you have access to). As a loan officer I saw many younger people with poor credit scores who always paid their bills on time -- their rent, utilities, perhaps the balance on a $300 "starter" credit or store card; but despite a poor score it was pretty easy to prove they were responsible with their debt management and get them approved for mortgages.

Today though you might not be able to get a loan even if you are very careful with credit.

That's because there are credit score minimums that are hard and fast and there is no room for an override even when it makes sense to do so. And to make things tougher, FHA may only require a score of 580, but most lenders require your score to be at least 620 or 640.

People who rent are at a disadvantage

When you have a mortgage it's easy to increase your credit score by paying it on time. It's considered an important account and your payment history on your mortgage is weighted more heavily than your history on credit cards or other consumer loans. But those who rent may pay just as much each month but they don't get the benefit of the inclusion into their credit scores. This again makes it harder for some who have a good payment history to get a good score and a mortgage.

On-time rent payments will soon boost credit scores.

According to the National Multi Housing Council, there are nearly 96 million renters who are not getting the "credit" they deserve based on their credit reports. In the past, on-time rental payments did nothing to boost a credit score. Positive rental history will now help many renters who are looking for ways to build or rebuild their credit scores. Experian has announced it is now incorporating positive rental data from its RentBureau Division into the traditional credit file, opening a new avenue for consumers like college students and recent graduates or immigrants to build credit with continuous on-time rental payments.

Pay your rent on time!

So now that your rent can boost your credit score, it's up to you to make sure your rental payment history is worth seeing. Your mortgage approval may depend on it.