An informal denial usually means that Social Security thinks that you are not eligible for disability benefits. This is different than being denied because Social Security thinks you are not disabled.

For example:  you, your spouse, or your household makes too much money or has too many assets.  This results is a financial denial. This sometimes happens in Supplemental Security Income (SSI) cases where, in addition to be disabled (unable to engage in a Substantial Gainful Activity, e.g. full time work), you also have to prove financial eligibility.

Another possibility is that you have not worked long enough (and earned quarters of coverage) to qualify for benefits, or you do not have quarters of coverage within the right time period to qualify for benefits.

In both examples the problem is eligibility:  Social Security does not think you can even get your foot in the door.

The flip-side of this, is that Social Security is not even considering whether you are medically disabled. They are not even getting to that step of the analysis.

If you disagree with the informal decision, the general recourse is to request a formal decision. The informal decision will tell you exactly how to do this, for example, by completing the application process or submitting a form.

Since Social Security is denying your case very early on in the review process, you may want to review your case with an attorney to see if there is a significant problem with your eligibility. If not, the lawyer may be able to direct you in how to get over this hurdle.