It depends. Did the IRA custodian pay your spouse directly, or did you make the distribution yourself and give the funds to your spouse?
Typically, you would provide the IRA custodian a copy of your divorce decree. The funds would then be transferred into the other spouse's own IRA account. This would be a nontaxable event to the IRA owner.
If you made the distribution in your name, then review your divorce documents. Sometimes there are instructions for these types of tax issues. If the 1099-R is in the name of the IRA owner, then you may end up being responsible to pay the tax. You can also contact the IRA custodian to see if other options are available to you.
Generally, whoever received the IRA distribution is the person responsible for paying the tax. The owner of the IRA shouldn't pay tax on funds that were given to a former spouse as part of a divorce.
See this TurboTax article Getting Divorced for additional information.
