What to report as impact factor for a journal that had one the year I submitted my manuscript, but not in the year of publication? I had submitted a paper in a journal whose impact factor was .78 according to Thompson Reuters citation reports in 2013. My paper got accepted in that journal and was published in 2014. The journal did not receive any impact factor for the year 2014. Sometimes I have to mention the impact factor of my papers with them but I do not know how to find the impact factor for this particular journal (It had impact factor when I submitted but when published it did not receive any impact factor). Please guide me what impact factor should I use for my above mentioned paper.

I have same question for change in the impact factor of a journal from submission time to publication time. Thank you.
Quick answer: the safest is to give the IF followed by the closest year of estimation: IF 3.5 (2013). The wisest is to understand why the journal does not have an IF for 2014: did it change its name, was it withdrawn from the JCR (journal citation report)?  

Impact factors for one year can be available after a few months.  You can mention other sources like Scimago, that may have other figures (eigenfactor, etc).