How to enable invoice items?

I have two businesses set up and on one of them I am now trying to set up invoice items and cannot find it under settings. The other one has been set up for a while and is ok. What am I not doing?

If you don’t see some module, you need to enable it.

To enable Sales Invoice Items, go to Settings tab, click Customize button and tick Sales Invoice Items

Thanks Lubos, that did it. I guess I had a senior moment and forgot.