I am assuming you mean business partner and not life partner. If it is business partner that you are working with on that trip...

I have had to do this a few times each year. Usually they ask my company name at check-in and when I say my company instead of the customer there is some push-back until it is explained that I am working/visiting the other company. If you are concerned, reach out to either your customer or the hotel to ensure you can use the rate and that there would be no issue. Only three times fifteen years did I have an issue...

• Once at the Downtown Brooklyn Marriott the customer had such a good rate that they had to send a letter to the hotel ahead of time letting them know I was entitled to use the rate. My contact knew this, told me ahead of time and arranged for the letter to be sent. When I checked in the clerk asked some questions to confirm that it was me and mentioned the advance authorization.
• Once we used our customer's rate at the Franklin TN Marriott. A salesperson made the reservation. I did not know at the time it was with the customer discount. Someone from the customer company called me the day before arrival asking who I was visiting at the company the next day. Apparently the company was provided the names and tried to figure out who I was supposed to visit because I was not on their list.
• Once at the Pattaya Marriott I used our corporate discount. The company has a large facility nearby that has nothing to do with what I do or my division. When I checked in I was asked many questions until they told me the facility was wondering why I was there. The rate was honored. Later I confirmed with our travel dept that the rate could be used by employees on vacation, but I never used it again.

If you mean life partner he/she will need to reach out to your company and see if employees' family members can use the rate and, if so, how.