How do I show that I got an exemption from the individual mandate?

Post enrollment issues | Individual Health Insurance

If you received an exemption from the Marketplace or are claiming an exemption while filing your taxes, you should complete and return IRS Form 8965 with your tax return. Note that if you received a Marketplace exemption, you will need to note the Exception Certificate Number (ECN) you received from the Marketplace on Form 8965. (IRS, About Form 8965, Health Coverage Exemptions).

Individuals with no coverage
Individuals with coverage
Coverage for small employers
Post enrollment issues