It would be nice to have a link to the basket from the invoice (right now it's just the receipt page) and a link from the basket to the invoice.
The link is at the invoiceline level (aqorder) - there is no logical link at invoice/basket level Looking at actual invoices being received on systems each line may be derived from a different basket. Similarly each orderline of a basket may appear on a separate invoice. So I assume this is just for better navigation along those links
*** This bug has been marked as a duplicate of bug 28449 ***