How to attach a letter from the UK showing the client is not subject to US self-employment taxes under the international treaty (and how to input that into Proconnect

[MidwestTaxGal]

My client has been a dual citizen and lived in the UK for more than a decade. They only just returned to the US and all of their income through last year should be covered under the US / UK treaty that says if you pay self-employment taxes abroad you aren't required to pay them here.  My client has submitted the request for the letter from the UK confirming their side, but we need it to be attached to the taxes and for ProConnect to reconfigure the taxes without adding that self-employment tax.  What is the best way to input into the system the fact that the taxpayer is excluded from self-employment taxes on their Schedule C under a treaty and that the documentation is attached?