Hi, First of all, thanks for accepting me to this group. I have a client I have worked with for a long time - my best client - who has recently said I must provide a PO number for every job I do for them on my invoices. So far, the various account handlers at this client have been providing a PO number during the course of the project or at the end. However, there is one who is ignoring my emails requesting the PO number. The project took several days and was finished several weeks ago, but I haven't billed for it, as I've been told I must have the PO number. I have flagged up the problem to the Traffic Manager (to whom I send my invoices), but nothing has happened. Does anyone know where I stand legally? Surely if the work's been done and accepted they have to pay for it? Can/Should I invoice anyway? If anyone can point me to any official information on this matter, I'd be really grateful.