Option and notes fields after cart at checkout for order, not just line items My client has gift wrapping services but they apply to the entire order, not one single line item. 

How would I add notes or custom fields to the entire order, at the shipping stage of checkout? is this possible without a plugin?

I tried to apply notes and giftwrapping options to the first line item by using the commerce/cart/updateLineItem form, on the cart.lineItems.first() but it didn't work. I presume that after the user proceeds to checkout the line Items no longer exist?
First, add a custom field to your orders, let's call it orderNotes.

Then, in any updateCart form, you can use an input with name="fields[orderNotes]" to set the value of that field.

(Line items persist on the cart until the end of checkout.  At that point they become a saved snapshot of those line items on the completed order.)

&lt;form method="POST" &gt;
       {{ getCsrfInput() }}
       &lt;input type="hidden" name="action" value="commerce/cart/updateCart"&gt;
       &lt;input type="text" name="fields[orderNotes]"&gt;
       ...etc