Assuming you meet other eligibility requirements, you can shop for coverage on the Marketplace during open enrollment or a special enrollment period if eligible, but if you have access to job-based coverage, you might not qualify for premium tax credits.
When people are eligible for employer-sponsored coverage, they can only qualify for Marketplace premium tax credits if the employer-sponsored coverage is unaffordable. The way this is calculated, coverage is unaffordable only if your cost for coverage for a single person under the employer plan is more than 8.39 percent of your household income in 2024 (for 2023, it is 9.12 percent of household income). (IRS Rev. Proc. 2023-29.)