If one is single when the unpaid tax liability accrued, only the one who incurred the tax debt is responsible for paying those taxes.  The IRS cannot take the other spouse’s property or levy her income to pay those taxes.  They might try to make the non-responsible person use her property as collateral to get a loan, for instance, to pay the taxes.  However, she is under no legal obligation to encumber her assets to pay the responsible person’s tax debts.  Also, the IRS cannot force her to use any of her income to help the taxpayer pay any part of the taxes.  However, if the taxpayer and new spouse buy real property together, the IRS can place a lien on the property.  That lien would encumber one half of the property (the liable party’s undivided one half interest).  If the situation escalated to a seizure and sale of the property, the IRS would get one half the value of the property (up to the amount of the tax debt) and the non-liable spouse would get the other half.