You pride yourself on your credit score, but was denied a mortgage. Here's why you might not have been approved.

1. Your income is too low for the amount you want to borrow.If you're securing a mortgage, you have observed that your prospective lender is assembling financial information about you. One data point it's specifically concerned with is your income. Your housing expense ratio must be balanced to ensure that your monthly mortgage payments will be affordable.

2. Your debt-to-income ratio is too high.When you're applying for a loan, your bank is going to carefully assess your debt-to-income ratio. This is a gauge of how much you are paying in monthly obligations relative to your income.

3. You're self-employed or have an irregular income.Most banks desire a robust history of income and employment before granting a mortgage. If you are employed with a traditional office job, this might not be a problem. However, for applicants who are self-employed or who have an irregular income, qualifying can be more difficult.Lenders might see this as a risky loan. Although you might have a great track record with paying your bills on time and in full, if the lender believes there's a possibility that you could lose your income, you may get denied.To strengthen your chances of approval, retain detailed records of your income and employment history. Additionally be prepared to turn over tax documents to prove you're a good earner.