Can I update a past completed trade to add the buyer?

Can I update a past completed trade to add the buyer? I'm a pretty new user to this site and have just realized I may not have credited the buyer in my trades. I've been looking around the site but don't think that its' possible.

If I remember correctly:
You can't but you can ask a mod to do it for you.

If more than 3 days have passed since you marked the item as sold, then no.

If you sold it in the last 3 days, message me with a link to the trade listing, and let me know what the diablo2.io username of the buyer was, and I can fix it for you.