I have a half fare card. Say I went one way to Paris. Then bought a ticket in Paris on a SBB train back to switzerland. Can I get the half price discount somehow?

You can buy the ticket online from http://www.sbb.ch/ and print it out yourself.

Doc.

but no way to get the discount at the train station, right? or can i send a receipt to the SBB afterwards and get the discount?

You can only get discounts on trains that cross the Swiss border.

Since you are in Paris, this case applies.

I'm pretty sure you only get the half fare on the portion of the trip inside of Switzerland.

I got it yesterday from Milan - Zurich and bought the ticket in Pisa. They looked at the halbtax a bit strange at first but then gave the discount no problem.

Trips abroad: 25% cheaper with the Half-Fare travelcard.

Your Half-Fare travelcard entitles you to a 25% reduction on the international sections of cross-border journeys to Germany and Austria, provided that you buy your ticket in Switzerland.

source: http://mct.sbb.ch/mct/en/reisemarkt/...btax-bonus.htm

There was another thread about this last year. I checked with SBB specifically about the Paris/Switzerland route and they told me there was only a discount on the portion of the journey within Switzerland.

One other point. Can you catch an SBB train from Paris? I thought all trains from Paris to Switzerland were SNCF.

Yes. There is a 25% reduction on trans-border travel when booked in Switzerland on trips to Germany and Austria. This discount does not apply to travel to France.