If in the divorce decree my ex-wife was to pay half of the taxes owed to the IRS but has made no attempt, how do I proceed to get her to pay?
Your recourse is to pursue contempt of court against your ex. You will need to file an Order to Show Cause for a hearing. Call the court clerk to schedule the hearing. List the date, time and department of the hearing in the Order to Show Cause. Also file your declaration signed under penalty of perjury stating the facts in support of your contempt of court claim and any additional supporting documents, evidence, etc. File a proof of service (court form). Mail a copy of all these court-filed documents to your ex to give your ex notice of the hearing. The proof of service verifies the date of mailing.
Prior to filing your documents with the court, ask the court clerk if any additional documents are required for contempt of court because the required documents may vary from state to state.