People who have health insurance are more likely to receive care and less likely to experience financial hardship or bankruptcy from medical bills. And thanks to the Affordable Care Act (ACA), the rate of uninsurance has hit a historic low of 10.5 percent, which means that more people benefit from coverage—but too many are still without it.

Today marks the beginning of the ACA’s annual new open enrollment period–the time when people who don’t have access to affordable health insurance through their employer can shop for and buy health insurance through the Federal Marketplace or their state-run Marketplace. With the push for people to enroll in health insurance over the next few months during open enrollment, it’s worth taking a closer look at who remains uninsured. A new report from the Kaiser Family Foundation examines this very question.

The report finds that of the 27 million people in the United States who are uninsured, more than 40 percent are eligible for help paying for insurance. The two forms of help available are insurance through Medicaid and Advance Premium Tax Credits (APTCs) that subsidize private insurance purchased through federal or state Marketplaces. The majority of people who are eligible for financial assistance are eligible for Medicaid (6.4 million adults and children).  While open enrollment gets a lot of attention, it’s important to note that people who are eligible for Medicaid can enroll anytime during the year

To be eligible for either APTCs or Medicaid, applicants must meet certain criteria. In general, people are eligible for Medicaid if they have annual income less than 138 percent of the poverty level and live in one of the 31 states that has chosen to expand Medicaid. In non-expansion states, parents lose Medicaid eligibility at much lower income levels, and adults without dependents are not eligible at all unless they qualify based on age or disability.

Those who do not qualify for Medicaid are eligible for APTCs if they earn between 100 and 400 percent of the poverty level. These subsides, which are provided directly to insurance companies, are calculated based on the enrollee’s estimated income. Eighty-five percent of all people who purchase health insurance through the Marketplaces receive APTCs.

One reason people remain uninsured even when they are eligible for assistance is they do not realize they qualify for financial assistance. With more than 40 percent of the uninsured population eligible for some type of assistance, it’s important to keep spreading the message that assistance is available. When it comes to Medicaid enrollment, states have several options to use data they already have to identify and enroll people who are eligible. The Kaiser report has state-level data about how many people fall into this category.  A concentrated effort to enroll eligible people in Medicaid will result in a significant decline in the number without health insurance and lead to more historic gains in health insurance coverage in the next few years.

The Kaiser report also finds that 2.6 million of the uninsured are not eligible for financial assistance because they earn too little to qualify for APTCs, yet their state has not yet expanded Medicaid. These people fall into the “coverage gap” –too poor for ATPCs but not eligible for Medicaid.  States could go a long way to covering these 2.6 million people by taking the option in 2017 to expand Medicaid.