Are unmarried domestic relationships able to share a health coverage plan? If so, are there any specific requirements for qualifying for it? (For example, living together a certain number of years, sharing a lease/mortgage, joint bank accounts, etc…)
My partner and I are interested in getting coverage together, and as far as I’m aware, my employer does not allow unmarried partners to be added to the plan, so we are looking at other plans available.
The Affordable Care Act doesn't require unmarried domestic partners to be included in family plans, but many insurers, state marketplaces, and employers offer to cover domestic partners in family plans. Unfortunately, there are some tax pitfalls because the law has tax implications for those in your federal tax family which doesn't recognize domestic partnerships. These includes: premium payments for covering a domestic partner on employer sponsored coverage being counted as taxable income, not being eligible for Premium Tax Credits on your partner's behalf (see Question 6), and the partner's plan MAY not qualify for COBRA.
Healthcare.gov recommends only including domestic partners in a family plan if you have a child together OR you can claim them as a tax dependent. Being able to claim a domestic partner as a tax dependent on your federal taxes isn't impossible, but it does essentially require actual financial dependence of one domestic partner on the other. Here is more information about domestic partners with regards to federal taxes from the IRS.
As for ObamaCare's exchanges and cost assistance, domestic partners cannot get cost assistance on a family plan together. This is because you are only eligible for Premium Tax Credits for yourself and those who you claim as dependents on your tax return (the only exception is adult non-dependent children under 26). As a rule of thumb it is smarter and a safer bet to qualify based on individual incomes unless you have children together, but at the end of the day the option that you decide is best for you and your family will affect how you file federal income taxes. If you are eligible to file together you will be able to claim cost assistance together. If you don't file together then you should apply for cost assistance separately.
Some insurers may be willing to sell private health plans as family plans to domestic partners, for instance you can check with a major insurer like Blue Cross Blue Shield to see what options they have. Often major insurers will let you customize non-group, non-Marketplace, private plans. As long as you have minimal essential coverage you have met the provisions of the Individual Mandate, regardless of where that coverage was purchased.
There rules apply to same-sex and opposite-sex partners.
You can learn more about ObamaCare and domestic partners here.