You as the cosigner and the other applicant on a car lease are equally responsible. You have the same responsibility for making payments -- just as you have equal rights to use the car. If the borrower of the car defaults the payment, each of your credit reports will show late payments.
Duration of Lease
When you enter the lease agreement as a cosigner, you are responsible during the entire period of the lease of the car. In some instances, you may remove your name from the agreement, but your cosigner, as well as the finance and leasing companies must agree to this. If the primary driver fails or refuses to pay, you should start paying to avoid damaging your credit score.
Maintenance of the Car
You have the same obligation to maintain the car as the primary borrower. If the principal borrower fails to maintain and repair the car, you will have to pay, as it is a shared responsibility. If the car is not maintained, the leasing company will impose charges at the end of the lease. If the primary borrower -- and you -- fail to pay the charges, it will affect both of your credit scores.
A third party can be used to pay off the debt when the primary and the secondary borrowers fail to pay. You and the primary borrower can use a debt-consolidating company that will take on the risk of paying the loan. The car will still be in the name of the primary borrower, as well as in your name as the cosigner. The leasing company holds the title, so you cannot repossess the car if the primary borrower fails to make payments.
You can arrange with the primary borrower to take over the lease, but the leasing and finance companies must also agree. If you as the cosigner are unable to make a current payment on the lease, inquire if the finance company offers a forbearance. If so, this may provide you with a temporary reprieve for a month or two.
The vehicle must be driven within the stipulated mileage in the lease agreement. If the primary borrower exceeds the mileage and fails to pay, you as the cosigner will be responsible for any extra charges. The over-mileage fees will be posted on your credit reports, if you don't pay, and may adversely affect your credit score.