If the IRS rejects your OIC application, you may choose to appeal that rejection within 30 days. To make this IRS appeal, you’ll need to use Request for Appeal of Offer in Compromise, Form 13711.
If your appeal doesn’t work, and you still can’t pay the full amount of your tax liability, you still have some tax debt relief options. You could choose to apply for a payment plan or you might be eligible for Innocent Spouse Relief. A tax professional will be able to go over all your tax relief options to find the one that works best for you.