For Undebt.it to work correctly, you need to be able to at least pay the minimum amounts due on all of your accounts. Let's say you have a monthly budget of $1,000 and the total minimum payments due on your debt accounts is $900. Then you decide to add another debt account that has a $150 monthly payment. Undebt.it will automatically increase your budget to $1,050. If you are unable to pay the minimum amount due on an account, then you need to exclude it from the payment plan. There is a setting in My Account > Profile Settings called "Auto Budget Adjustment" where you can turn this off if you like.