We reluctantly ask you for an extension of payment of your invoice no. …
We are sorry to inform you of the delayed settlement of invoice no. …
Due to circumstances beyond our control, we are at the moment unable to …
We will clear your invoice as soon as possible.
We will settle our account before the end of this month.
We trust that you will understand our precarious situation.
We will make a determined effort to avoid similar inconvenience in the future.
Hoping that you will grant this request, …