What documentation is required to request a hardship exemption from the requirement that I have health insurance or pay a penalty?

For the 2018 tax year, you can claim a hardship exemption directly on your tax return instead of applying to the Marketplace for a hardship exemption.  If you experienced a hardship that prevented you from obtaining health insurance in 2018, you can simply check the box on the front of the federal Form 1040 indicating that you qualify for an exemption.  You will not be required to submit documentation with your tax return, but should retain any documentation of the hardship for your own records.