[mothered]

I used the partial refund. I ordered four shirts and some cuff links. I said that only the cuff links and one shirt came. Does this change whether I should provide the invoice or not?

I see. Still, don't provide the Invoice.  

Do not allow any Indication that the Item may have been received. As far as you're concerned, they neglected to send the Item and the Invoice.

Brilliant, thanks for the advice. I’m learning everyday and I hope for this to be the first of many SEs.

You're welcome.

If you get a moment and don't mind sharing your experience with this particular SE, I'd be Interested to read It's progression and/or outcome.
If not, that's fine.