http://www.irs.gov/publications/p925/ar02.html#en_US_2010_publink1000104565
If you meet any of the exceptions listed above, see the instructions for Form 8582 for information about how to report any income or loss from the activity.
If you are married, filing a separate return, and lived apart from your spouse for the entire tax year, your special allowance cannot be more than $12,500. If you lived with your spouse at any time during the year and are filing a separate return, you cannot use the special allowance to reduce your nonpassive income or tax on nonpassive income.
The maximum special allowance is reduced if your modified adjusted gross income exceeds certain amounts. See Phaseout rule, later.
Example.
Kate, a single taxpayer, has $70,000 in wages, $15,000 income from a limited partnership, a $26,000 loss from rental real estate activities in which she actively participated, and is not subject to the modified adjusted gross income phaseout rule. She can use $15,000 of her $26,000 loss to offset her $15,000 passive income from the partnership. She actively participated in her rental real estate activities, so she can use the remaining $11,000 rental real estate loss to offset $11,000 of her nonpassive income (wages).