So here is the hypothetical. Say you're a company who does a portion of your work in the automotive sector. You are a sub tier supplier. You have one main customer who strongly suggests you to be TS 16949 registered. So you obviously do it for them. But you have a couple of others whose products may have automotive applications (they may be service or aftermarket or a combination) but don't request or require TS registration. Lets say they have never really address certification and you have never done a full AIAG PPAP on their parts. Looking at their sales volume you can determine TS is overkill - i.e.; not worth the trouble. Do you need to included them in your TS system?