Only people whom the IRS "considers unmarried" qualify to file as head of household. If you have a spouse, this means you must be either legally separated or you must have lived apart for the last six months of the year. You and your spouse would have to file separate returns, and you would have to meet other head of household requirements. If you do qualify as head of household, your spouse can claim a standard deduction on her own return.
Head of Household Status
If you and your spouse were married and living together on December 31 of the tax year, you are not head of household. If you are married, you and your spouse must have lived in separate residences from at least June 30 through December 31. You must also have paid more than 50 percent of the expenses for maintaining your own home.
You must also have at least one dependent -- such as your child -- to qualify as head of household. However, you don't actually have to claim a dependent deduction for your child -- you simply have to be eligible to do so. For example, if you're legally separated, your decree might order or stipulate that you and your spouse will trade the dependent exemption for your child yearly: perhaps she takes the deduction in even-numbered years, and you take it odd-numbered years. In this case, you could still be head of household in even-numbered years because, absent the terms of your decree, you would have been able to claim your child as your dependent.
If you've filed for divorce but the divorce isn't final yet, the same standards apply. For example, if you've been living separately but your divorce isn't final yet, you must typically file a joint married return or a separate married return, unless you qualify as head of household. Neither you nor your spouse can file as single taxpayers, because you’re not legally single yet.
The Standard Deduction
If you don't qualify as head of household, and if you’re still legally married, your spouse can only use the standard deduction if you do so as well and don't itemize your deductions. Because head of household status means the IRS considers you unmarried, this rule no longer applies if you qualify.