You can still make delivery note of non stock items and get is signed from customer to document that software has been delivered. It doesn’t pass any financial entry as it is non Stock item.
We make delivery note for both types. Helps us in future when client asking for free support. Good to inform them that project has been closed and now they need to pay for support.
On some system, they have a category for items to be delivered or not. It is same as what the checkbox of “is Sales item” and “is purchase item” works. The checkbox can be included on the section for both purchase and sales details; to access if mandatorily included the for delivery note or purchase receipt. It can also be the triggered for closing of the document since it will add as another work for service industry to closed the documents manually instead of the system closing it already.