If it is a journal for which we have online access, locate it using the 'Searchable list of e-Journals' on our e-journals page (i.e. not by using Search the Library Catalogue for e-Journals):
Click on the journal title in the list (not on any of the full-text sources listed below it) and you will see an SFX screen that offers a link to the Impact Factor:
This takes you to the full Impact Factor report for the journal on Journal Citation Reports (ISI Web of Knowledge).
You will see an Impact Factor link offered on every SFX screen for any journal that has an impact factor. So if you want the Impact Factor for a journal that we can't access online, just find an article in it in a database that offers find it @ liverpool links (most do!) and follow that link.
Where a journal appears in both the Science and Social Science editions of JCR we just offer a link to the Science Edition to avoid offering two links to the same information. The actual Impact Factor is the same in both editions!