WASHINGTON -- Congress is nearing the finish line on tax reform legislation, but some say they're concerned the final bill could also mean the end of the Affordable Care Act as we know it.

The Senate's tax plan repeals the individual mandate, a tax that punishes people who don't buy health insurance. It's a key pillar of the Affordable Care Act.

Repealing the individual mandate isn't part of the House's plan, but tax writers say they're expecting the measure to make it into the final piece of legislation. Some health care experts say with no mandate, healthy, younger people will forego health insurance altogether or will purchase less-extensive, less expensive policies outside of the insurance marketplace.

Others also fear that this will cause premiums to rise for people still using the Affordable Care Act. However, people who receive subsidized health insurance won't be affected by the repeal of the individual mandate since the price of their insurance premium is limited to a percentage of their income.

Regardless, some health care leaders say after Congress' failure to kill the Affordable Care Act, this is simply an attempt at crippling it.

"The Affordable Care Act is working, we simply need to improve it. Undermining it is not the answer,” said Elizabeth Colvin, with Insure Central Texas.

Meanwhile, Republican Senator Susan Collins says in return for her vote on the tax bill, she's been promised legislation that would send billions to states to establish high-risk pools and that could help lower premiums.