I'm finishing my PhD; I will be defending in a few weeks and then starting a postdoc at a high-profile university/lab. One of my research students has asked me to write a letter of recommendation for him which is due by the end of this week. His other letter writers are also at my current university. I'd like to put my new affiliation on the letter as part of my signature since I think it would add some diversity to his letters and maybe make it look a bit more impressive than yet another letter from our large state university. Two questions: is it OK to add this new affiliation? I haven't started the job yet, but I've signed a contract and they have told me to add the affiliation when applying for conferences starting in the next months. And if it is OK to use it, how should I put it? Including my current university, I assume? Not really sure how to sign these things; it's my first time writing a real letter of recommendation. Thanks for the help.