Courrier-type - Relance pour impayé (action en justice éventuelle)

Dear [Mr or Mrs or Sirs], We wrote to you on [date], [date] and [date], reminding you to settle your invoice [références], dated [date]. Today, we have received no reply to these letters and ask you to give this matter your prompt attention and send us a cheque by return of the post. We must inform you that if we do not receive the full payment of this invoice by [date], we shall have no choice but to contact our solicitors in order to take legal action against you. Believe that we regret to be thinking of this eventuality. We look forward to receiving your cheque. Yours sincerely [votre nom] [votre fonction]