Deadline for Citi Business

[Swatch]

A few days after my cc application, they asked me to send documents. It said I would have to take action by a certain date. Would it be ok if I postmark by that date, or do I have to send days before? I'm waiting on a bureau, otherwise I would reply now. 

[FinStar]

It is my understanding that they need to be in possession of the documents by X date otherwise the application will close out. They don't go by postmark.