How much difference does a single line on a tax form make? For Obamacare's individual mandate, the answer might be quite a lot.

Following President Donald Trump's executive order instructing agencies to provide relief from the health law, the Internal Revenue Service appears to be taking a more lax approach to the coverage requirement.

The health law's individual mandate requires everyone to either maintain qualifying health coverage or pay a tax penalty, known as a "shared responsibility payment." The IRS was set to require filers to indicate whether they had maintained coverage in 2016 or paid the penalty by filling out line 61 on their form 1040s. Alternatively, they could claim exemption from the mandate by filing a form 8965.

For most filers, filling out line 61 would be mandatory. The IRS would not accept 1040s unless the coverage box was checked, or the shared responsibility payment noted, or the exemption form included. Otherwise they would be labeled "silent returns" and rejected.

Instead, however, filling out that line will be optional.

Earlier this month, the IRS quietly altered its rules to allow the submission of 1040s with nothing on line 61. The IRS says it still maintains the option to follow up with those who elect not to indicate their coverage status, although it's not clear what circumstances might trigger a follow up.

But what would have been a mandatory disclosure will instead be voluntary. Silent returns will no longer be automatically rejected. The change is a direct result of the executive order President Donald Trump issued in January directing the government to provide relief from Obamacare to individuals and insurers, within the boundaries of the law.

"The recent executive order directed federal agencies to exercise authority and discretion available to them to reduce potential burden," the IRS said in a statement to Reason. "Consistent with that, the IRS has decided to make changes that would continue to allow electronic and paper returns to be accepted for processing in instances where a taxpayer doesn't indicate their coverage status."

The tax agency says the change will reduce the health law's strain on taxpayers. "Processing silent returns means that taxpayer returns are not systemically rejected, allowing them to be processed and minimizing burden on taxpayers, including those expecting a refund," the IRS statement said.

The change may seem minor. But it makes it clear that following Trump's executive order, the agency's trajectory is towards a less strict enforcement process.

Although the new policy leaves Obamacare's individual mandate on the books, it may make it easier for individuals to go without coverage while avoiding the penalty. Essentially, if not explicitly, it is a weakening of the mandate enforcement mechanism.

"It's hard to enforce something without information," says Ryan Ellis, a Senior Fellow at the Conservative Reform Network.

The move has already raised questions about its legality. Federal law gives the administration broad authority to provide exemptions from the mandate. But "it does not allow the administration not to enforce the mandate, which it appears they may be doing here," says Michael Cannon, health policy director at the libertarian Cato Institute. "Unless the Trump administration maintains the mandate is unconstitutional, the Constitution requires them to enforce it."

"The mandate can only be weakened by Congress," says Ellis. "This is a change to how the IRS is choosing to enforce it. They will count on voluntary disclosure of non-coverage rather than asking themselves."

The IRS notes that taxpayers are still required to pay the mandate penalty, if applicable. "Legislative provisions of the ACA law are still in force until changed by the Congress, and taxpayers remain required to follow the law and pay what they may owe?," the agency statement said.

Ellis says the new policy doesn't fully rise to the level of declining to enforce the law. "If the IRS turns a blind eye to people's status, that isn't quite not enforcing it," he says. "It's more like the IRS wanting to maintain plausible deniability."

Tax software companies are already making note of the change. Drake Software, which provides services to tax professionals, recently sent out a notice explaining the change in policy. As of February 3, the notice said, the IRS "will now accept an e-filed return that does not indicate either full-year coverage or an individual shared responsibility payment or does not include an exemption on Form 8965, as required by IRS instructions, Form 1040, line 61."

The mandate is a key component of Obamacare's coverage scheme, which is built on what experts sometimes describe as a "three-legged stool." The law requires health insurers to sell to all comers regardless of health history, and offers subsidies to lower income individuals in order to offset the cost of coverage. In order to prevent people from signing up for coverage only after getting sick, it also requires most individuals to maintain qualifying coverage or face a tax penalty. While defending the health law in court, the Obama administration maintained that the mandate was essential to the structure of the law, designed to make sure that people did not take advantage of its protections.

In a 2012 case challenging the law's insurance requirement, the Supreme Court ruled that the individual mandate was constitutional as a tax penalty. The IRS is in charge of collecting payments.

Some health policy experts have argued that the mandate was already too weak to be effective, as a result of the many exemptions that are included. A 2012 report by the consulting firm Milliman found that the mandate penalty offered only a modest financial incentives for families making 300-400 percent of the federal poverty line. More recently, health insurers have said that individuals signing up for coverage and then quickly dropping it after major health expenses is a key driver of losses, and rising health insurance premiums.

It's too early to say whether the change will ultimately make any difference. But given the centrality of the mandate to the law's coverage scheme and the unsteadiness of the law's health insurance exchanges, with premiums rising and insurers scaling back participation, it is possible that even a marginal weakening of the mandate could cause further dysfunction. Health insurers have said the mandate is a priority, and asked for it to be strengthened. Weaker enforcement of the mandate could cause insurance carriers to further reduce participation in the exchanges. One major insurer, Humana, said today that it would completely exit Obamacare's exchanges after this year.

It is also possible that congressional Republicans will make it moot by repealing much of the law, including its individual mandate, which, as a tax, can be taken down with just 51 Senate votes.

Regardless of its direct impact, however, the change may signal that the Trump administration intends to water down enforcement of the health law's most controversial requirement, even if those steps are seemingly small. The Trump administration may not be tearing Obamacare down entirely, but it appears to be taking steps to weaken the law, however subtly, one line at a time.

Correction: The IRS did not reject silent returns last year, as this story originally indicated. The plan was to go into effect this year, for 2016 returns, but the IRS reversed course on February 3. Reason regrets the error.