It is advised to proceed with great caution whenever opening a joint credit card account with someone you are in a relationship with. While at the time it might seem like a good idea since you are very much in love and expect it to last forever, when the relationship ends you are left in a difficult position with no real legal recourse on unpaid credit card debt.
If you have a joint credit card with an ex-boyfriend or an ex-girlfriend you are just as responsible for the debt on the credit card even if you did not make the charges. When you cosign on a credit card as a joint account holder, the contract does not consider the nature of the relationship as pertinent to the terms and conditions which make you just as responsible to pay off the debt as the primary credit card holder.
If the relationship has ended and you are faced with a debt on the credit card non-payment will hurt your credit score as well as the joint credit card account will be reported on your credit reports as well. Negative information concerning nonpayment or a delinquent account will stay on your credit report for seven years and hurt your credit score for months or years.
Having ended the relationship with your boyfriend girlfriend does not provide you with a legal recourse to do away with the debt. If the other person has not paid off the balance and cannot be located then you should call up the credit card company and let them know what happened. Ask for the advice which in most cases will be to pay off the balance. This may be the only way for you to prevent damage to your credit score. Ask the credit card company to close the account if possible after payment.
In case you cannot pay the full amount try and settle the account with the credit card company and requested to be closed so that the balance does not increase and further charges cannot be made on it by your ex-boyfriend or girlfriend. Both missing the payments and settling the account will hurt your credit score differently but it will put an end to the debt from where on you can continue to build a positive credit history.