This sounds more like a question/discussion rather than a "feedback on the community forum". You may wish to move it, to get more responses.
Now, if I could just figure out how to do that…
You could set up a relationship of customers to orders using the customer number (which is hopefully on the invoice). Then put in a portal showing the order records from the customer record. Then do a search in the portal for order date within the last year to find everyone who has placed an order in the last year. Show omitted and you'll have the ones who haven't.
When you view this topic in the forum (not in your INBOX), do you see "Move" link to the right?
If you have a portal of orders in your customer layout you can search by date range e.g. 1/1/2016...2/15/2016 on the order date in the portal. This will give you all customers who placed orders this year. Then you can go to Records menu and use "Show Omitted Only" - this should give you all customers who did not place orders this year. If you are doing this on a regular basys you can script the whole process and attach it to a button.
I've just noticed that cable2001 posted the same suggestion much earlier. My apologies for double posting.
This will show customers that never placed an order, too, which is not what OP wants.
This will show customers that never placed an order
Yes, you are right.
I would run a calculation with FQL on the customer agains orders.
With the manual search you would need to reverse the search parameters and do not use the omit records (probably should have done it in the first place)
For the current year just use < 1/1/2016
For any other period you would need to use OR search
For the year 2015:
< 1/1/2015 in the order date field
Requests / Add New Request
> 31/12/2015 in the order date field
This should exclude the customers who never placed an order
I would use ExecuteSQL in a 2-liner script using a Custom Function, but OP is new to FM so I refrain from posting it. However, I know you want a clue, so here it is: https://www.briandunning.com/cf/926