If you add a domestic partner toyour policy, you must pay income taxes on the portion of the premium for your partner that your employer pays. (By contrast, you aren't taxed on benefits for a legal spouse or children.) So if your partner has insurance through his or her company, it's probably best to keep the two separate policies.
Then add up all those amounts and subtract 10% of your adjusted gross income (AGI) from that total to calculate your allowable casualty losses for the year.