MNsure is sending postcards to about 24,000 households in hopes of luring health insurance shoppers before a Monday enrollment deadline.

Most who bought coverage through the state's health insurance exchange for 2014 are in policies that will automatically renew outside of MNsure next year.

The mailing being sent this week is targeted to those consumers, and tells them cheaper options should be available through the exchange, said Scott Leitz, the MNsure chief executive.

The activity comes as MNsure is working to send electronic files to health insurance companies with information about those signing up through the exchange. The data must be transmitted before subscribers can get invoices for their coverage, as well as health plan ID cards.

Within the past week or so, MNsure sent more than 9,000 enrollment files to insurers, said Joe Campbell, a MNsure spokesman. But some files have missing or duplicate information, said Eileen Smith, spokeswoman for the Minnesota Council of Health Plans, a trade group for insurers.

"We're working to identify and help MNsure correct the inconsistencies," Smith said. Insurers found similar problems with MNsure enrollment files last year, but Smith said the situation is better this year because "we're working together on it — we're involved in this early stage of helping fix the issues."

Minnesota launched the MNsure marketplace to implement the federal Affordable Care Act, which requires almost all Americans to have health insurance or pay a tax penalty.

For the fiscal year starting July 1, 2015, MNsure expects to cover about one-fourth of its budget by withholding a portion of premiums for private health plans sold through the exchange. The budget expects MNsure to enroll next year in commercial policies about 67,000 people — a figure that is about a third lower than earlier targets, which were reduced from original projections.

As of Wednesday, 12,803 people had signed up for private policies for 2015 through the exchange, Leitz said. He said that MNsure doesn't have a particular goal for commercial enrollment by the Dec. 15 deadline, which applies to people who want coverage that starts Jan. 1.

Open enrollment stretches through Feb. 15, after which point people can buy policies through the exchange only in special circumstances.

In addition to new enrollees, MNsure projects about 37,000 people who bought through the exchange this year will return for coverage next year. Hitting the mark involves appealing to many subscribers with PreferredOne — the Golden Valley-based insurer that's currently the most popular option on MNsure, and won't offer coverage through the exchange for 2015.

On Thursday, Leitz said a new analysis suggests that PreferredOne customers who bought with a tax credit for 2014 could wind up paying 168 percent more if they renew current coverage rather than moving to the exchange. That's because PreferredOne premiums are on the rise, and tax credits are only available for those who buy through MNsure.

Inertia is often a big factor among consumers when it comes to buying insurance, and it's one reason MNsure has lowered its enrollment projections.

It's possible that many PreferredOne customers won't realize the financial stakes involved with not making a change, Leitz said, until they start studying bills for their January coverage. A spokesman for the insurer said Thursday that while renewal notices were sent in October, invoices are scheduled for the second half of December.

The timeline means that MNsure might see another surge in sign-ups, Leitz said, leading up to a Jan. 15 deadline for February coverage.

"Enrollment has been very strong," he said.

Insurers haven't yet sent any bills to people who have used MNsure to select a private health plan for 2015, said Smith of the Minnesota Council of Health Plans. The timeline for invoices to go out is unclear, but Smith said insurers aren't sounding any alarms.

Christopher Snowbeck • 612-673-4744

Twitter: @chrissnowbeck