Joe Carlson and Daven Ralston opened their Baltimore bookstore Charm City Books because they were “more interested in making a difference than a dollar.” But they still have to pay the bills — including health insurance.

“We wouldn’t have the shop without our exchange insurance; we wouldn’t have our daughter,” said Carlson, whose family of three is currently paying a $400 monthly premium through the state’s online health insurance marketplace.

But like thousands of others in Maryland, Carlson’s monthly bill is about to jump to $1,100 for the same coverage under the federal Affordable Care Act.

That’s largely because enhanced federal subsidies are expiring and Congress has deadlocked on a plan to extend them.

Monday is the deadline for millions of people around the country to enroll in a new plan for coverage beginning Jan. 1. But in Maryland, the state exchange opted to provide consumers a bit more breathing room through the end of the month.

Carlson and Ralston haven’t settled on a plan, and it’s likely to be a tough choice for many. Some will choose to pay more, while others may downgrade to a less expensive plan with fewer benefits and higher-out-of-pocket costs. And others may decide to forgo insurance altogether because of the price.

So far this year, Maryland’s exchange is reporting some positive and negative trends. While fewer new people have enrolled in any plan, fewer existing customers have officially dropped out, according to the Maryland Health Benefit Exchange.

Michele Eberle, the exchange’s executive director, said final numbers won’t be known right away because plans automatically renew unless people change or cancel them.

“We won’t know for sure until our consumers make their first payments in January to see who ultimately decides not to move forward with their health plan,” she said.

But Eberle does expect fewer Marylanders to drop coverage because of the state’s new subsidy program, which was created to offset some of the lapsing federal subsides. Consumers earning less than 400% of the federal poverty level — about $65,720 for an individual — can qualify for at least some aid. She urged people to see if they qualify.

“Maryland Health Connection is here to help,” she said. “Many high-quality, low-cost options are available.”

The majority of Marylanders get their health coverage through their employer, but close to 500,000 individuals, families and small business people buy their coverage through the state health exchange or directly through an insurer.

About 190,000 of them currently qualify for federal subsidies.

That’s not the only issue, however. Everyone will pay more for the plans themselves, including those with exchange plans and those with employer-sponsored plans, due to higher drug and other medical costs.

The average premium increase on Maryland’s exchange is about 13.4%, which is below the national average. But coupled with lost federal subsidies, average consumer bills could rise 50% or more.

President Donald Trump and GOP officials have said that enhanced subsidies were always supposed to be temporary. And the Congressional Budget Office estimates they would add $355 billion to the deficit over a decade. Federal lawmakers haven’t settled on a plan to ease consumer pain, and rejected the latest plan to extend the subsidies again Thursday.

Nationally, more than 24 million people have Affordable Care Act coverage. A recent poll from the nonprofit health policy organization KFF found a quarter of them would “very likely” go without insurance if their payments doubled.

State officials estimated that some 70,000 could drop coverage if they don’t have federal subsidies, a risky bet for them and a potential burden on the health care system that could lead to higher bills for everyone.

Margaret Dikel, a part-time orchestra manager from Montgomery County, said she plans to keep her plan until June, when she can go on Medicare, the federal health plan for seniors, and also enroll in a smaller plan to help cover out-of-pocket costs. But in the meantime, her premium was slated to nearly double to $1,522 from $806.

She planned to tap her retirement funds but then determined she likely would qualify for the new state subsidies. It would lower her premium to $931.

“I’m holding my breath until I get the first bill from CareFirst [BlueCross BlueShield] in January, but even then I’ll be on pins and needles despite going on Medicare in June,” she said.

Marylanders who don’t end up renewing their plans or were already uninsured can also check a box on their upcoming tax returns that triggers a state assessment of their eligibility for coverage through the exchange or Medicaid for low-income residents. Those who file by April 15 get another chance to enroll.

“It’ll be a lifesaver for many,” said Vincent DeMarco, head of the advocacy group Maryland Citizens Health Initiative.