>You could use the SoapExtension class:
>http://msdn.microsoft.com/en-us/library/system.web.services.protocols.soapextension.aspx
>http://msdn.microsoft.com/en-us/magazine/cc164007.aspx

That's right. I forgot about that one.

>This almost sounds as if they are asking that empty dates should be transmitted as null but are then refusing to accept it .......

Yes, this is exactly the case. I still haven't heard from the last communication with the client. So, I will have more info on this soon.

Thanks