An IVA (Individual Voluntary Arrangement) is as the name suggests, individual to you. However if any of the debts were taken out in joint names, the other party will also be fully liable for that whole debt.
Your own liability for the joint debt will be taken care of by your IVA; however, the creditor can also pursue the other party for the full outstanding amount. If you are jointly liable with your partner who is not entering into an IVA, an allowance will be made in your Income and Expenditure for them to repay the debt.