Pat Parman-Bethard, 61, a social worker, and Kristen Parman-Bethard, 54, a nurse, of Kent, partners for 20 years.

As Pat and Kristen Parman-Bethard's story shows, unmarried couples have to work harder to build a nest egg, as they don't enjoy all the financial benefits a married couple would.

Their goal: To each retire at 66 and live on half their current $100,000 income.

What they have: $5,000 in Pat's IRA; $51,000 in Kristen's supplemental-retirement plan at work, plus she'll have a pension of about $900 a month.

The problem: Because the IRS doesn't recognize their union as a marriage, certified-financial planner James Reitan of Kirkland says they face such extra financial challenges as:

• No inheritance: Unmarried couples can't inherit a deceased partner's Social Security, so the pair need to save aggressively to make up for retirement income they might lose if one of them dies prematurely.

• Required withdrawals: IRAs and other retirement accounts may require a nonspousal survivor to withdraw the money rapidly, rather than being able to use the assets to generate retirement income as a spouse could.

• Nothing automatic: Life insurance and retirement accounts won't automatically go to a partner, the way they would with a married couple, so they must regularly review accounts to make sure they have named each other as beneficiaries.

• Longer life: Women statistically live longer than men, so they must plan for more retirement years than a traditional married couple.

Steps to take: Refinance their higher-interest debts, including car payment and second mortgage on their condo, into a low-interest first mortgage. This generates enough savings to invest so that, by Pat's 2011 retirement, the couple could have an extra $100,000.

Good thing Pat plans to keep working part time in retirement, says Reitan: Without that $7,500-per-year income, he gives the plan only a 75 percent to 80 percent chance of success.