I need this answer as well. Seems to be blank on some occasions, but haven't been able to figure out when, why or how it happens. It would be nice to default it or know when it is set to blank. I've even tried to set up a phony order with a blank ship date and copy it. That doesn't work either.

I am guessing here, since I have not seen this issue before, but

check menu edit>preferences and see if you have a check mark to prefill transactions with previously entered content.  Sorry I can not remember off hand what left side choice it would be under or if it is on the company my pref tab

It sounds like that is what is happening, for that customer it is recalling the previous transaction information

I've already looked on the preferences and there is nothing there specifically for that. I does come up blank or null at times but not all the time. Yes it seems like it remembers the last transaction, but not always...When it's filled in, I don't know how to clear it, so I just work around it, shut it down or restart and try again.....and sometime it is clear and sometimes it's not....JUST NOT SURE!

to clear it, have you tried clicking in the field and deleting the entry?

Are you by chance sometimes using a memorized transaction, or using an old transaction and duplicating it, if so that might be where it is coming from