To view which user created a particular invoice simply search for the invoice number in the top left search box and click on the invoice description to bring up the details.
Once you're on the invoice screen click on the + icon next to 'Job Address Details' and expand the area.
In this section look for 'cleared on system by' and a users name. This is the user who invoiced/cleared the job.
You will also see the date/time below which tells you exactly when the invoice was created.