The filing status is determined based on your married status as of the last day of the year, i.e. whether you were still married or divorced on 12/31/08. If you were still married, you should file married filing separate. If youwere divorced, you could file as "single" or a "head of household" if you meet the necessary requirements. You can read IRS Publication 501at www.irs.gov, it gives all the answers about the filing status and dependents.
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