Any reply thanking the person for sending the document will confirm that you have received it so saying you’ve received it in your response would probably sound odd and redundant. What else you would say would depend on what you are expected to do with the document and would very heavily on exactly how formal you need to be. Also how you thank them would depend on how much work they put into the document. If they simply sent it to you and didn’t produce it, a simple Thank you might work. If they spent a lot of time on it you may thank them for the work they did. Lastly, you would probably use a name for the document or describe it depending on what it is, instead of saying “the document”. So here are some possibilities: Thank you for attaching the loan documents. I will review them and respond with my recommendations. Thank you for your work on the affidavit. I will confer with John and we will keep you informed of any recommended actions. To give any more specific advice we would need to know more details.