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A two-person plan needs four things: a joint or separate filing status, a partner profile with birth year and life expectancy, an owner on every account, and a recipient on every income stream. CoastMath then applies each person’s own age and limits to what they own and earn, and computes one household tax return each year.
- In Plan details, choose Filing status. For Married Filing Separately, also check Lived apart from spouse for the entire tax year if it applies; it changes how Social Security is taxed. Enter Children’s birth years for the child tax credit; see Federal brackets, deductions and indexing.
- In Partner and estate, check Plan includes a partner (already checked when the plan was created with Planning with a partner) and enter Partner birth year, Partner birth month and Partner life expectancy (age). Click Save estate settings.
- In Accounts, set Owner on each account to Primary person, Partner or Joint.
- In Income streams, set Income recipient on each salary, pension and Social Security stream to Primary person or Partner.
- Back in Partner and estate, choose the Plan ends and Filing status after partner’s death; see When a partner dies.
Ownership decides whose age and limits apply. CoastMath tracks each partner’s age every year from their birth year.
| Rule | Follows |
|---|---|
| IRA, 401(k) and HSA contribution limits and catch-ups | The account owner’s age and earned income; on a joint return, IRAs can use the couple’s combined earned income |
| Required minimum distributions | The account owner’s age and birth year |
| Early-withdrawal penalty before 59½ | The account owner’s age |
| Social Security claiming age and start | The income recipient’s age and birth month |
| Social Security payroll tax wage base | Each earner’s own wages |
| Income that stops at death | The income recipient |
Joint accounts can’t hold IRAs or 401(k)s and don’t receive retirement-account contributions. For rules that need an age, a joint account uses yours.
See Contributions, employer match and limits, Required minimum distributions and Social Security benefits for each rule.
Each year CoastMath computes one federal return, one state return and any local return for the household, with all income entered in the plan. The filing status selects the brackets, standard deduction, capital-gains thresholds, Social Security taxation thresholds and other status-dependent limits. Taxes that apply per person, such as the Social Security payroll tax, are computed per person first.
Add a Filing status change in Plan details for a year or milestone. Your marital status at year end controls that entire tax year: a marriage in December changes that year’s filing status. Later scheduled changes apply in date order; the last listed change wins if dates match. Death-driven changes take precedence after a death. See How CoastMath calculates income tax.
The Overview lists a household-mismatch warning when the plan is inconsistent:
- an account or income stream belongs to a partner, but the plan has no partner profile;
- the filing status is Married Filing Jointly, but the plan has no partner profile.
Removing a partner doesn’t move their accounts or income. Reassign them first under AccountsOwner and Income streamsIncome recipient.
For what happens when a partner dies, and how survivor benefits are handled, see When a partner dies and Spousal and survivor Social Security.