You mean you need to have a second sheet that is laid out just like the
first?  Simply right-click the first sheet's tab and choose [Move or Copy]
from the list.  Indicate where you want the copy to appear and be sure to
tick the "Make copy..." option.

If you're going to need to add many such sheets to the same workbook, I
suggest starting off with an empty one, make a copy of it so that there is an
'empty' copy of the sheet always available to copy to a new sheet and start
another envoice fresh from.