Academic affiliation on papers written while between jobs There have been many questions in the past about choosing an affiliation to write on your papers. This one has a nuance that is a bit different from having two jobs.

I am currently between two jobs (PhD student and postdoc) and currently not academically affiliated to either. I am currently writing a paper and I am trying to figure out if I put my PhD affiliation or my postdoc affiliation.

The reason for the PhD affiliation is because a lot of the work was done there.

The reason for the postdoc affiliation is because then anyone could contact me for correspondence with respect to the paper.  

I feel there must be a hard and fast rule to this, so I was hoping someone could enlighten me. 

Thanks!
I suggest using the postdoc affiliation (precisely for the reason you mention and also because you will probably still be there while the paper will be reviewed) and thanking for support the university where you did your Ph.D. in the acknowledgments.