It is *possible* that  you could establish that a combination that of you detailing how much you could pay in writing to them, and then them demonstrating acceptance of that amount or  payment plan by cashing the checks without complaint--ast least for a time--constitutes and evidences an agreement between you and them as to a payment plan. However, be aware that without something more explicit from them demonstrating or stating acceptance, that is an uphill battle for you--it is far from definite that you would prevail. That is because the debtor does not have the right to unilaterally determine how much he or she will pay, and when someone owes a debt, the creditor is generally allowed to accept partial payments towards that debt without compromising its abiltity to proceed against the debtor for the balance of payment. In most cases, therefore, the creditor cashing your checks does not, by itself, show that they accepted the payment plan and agreed to it; the fact you laid out the plan in writing helps, as does that they seemingly demonstrated acceptance of the plan for a period of time. However, as noted, it is far from definite that you can prove there was an agreement as to the payment schedule. Without an agreement, they can seek all the money at once.