Your profit and loss report may be confusing if your costs are recorded in
one period and your revenue (or invoice) is recorded in a different time
period. If that happens, your financial statements may show a lower than usual
profit margin in one period and a higher than average profit margin in the next
period. This issue is typically referred to as a timing problem.
If you want to avoid this issue, you can create the QuickBooks invoice for
your customers when you receive the products from the vendors or as soon as you
are finished building the goods.