The Upper Tribunal have recently handed down a judgement in the case ofFetle (Partners: two year requirement  UKUT 00267) (IAC). This is a useful authority for certain categories of people making an application to join or remain with their partner in the United Kingdom and who may not have lived together for a minimum of two years.
This case distinguishes between the Immigration Rules for those applying for entry clearance as the partner of a recognised refugee, and those making an application as a partner under Appendix FM of the Immigration Rules (i.e. as a partner of a British citizen or those with settled status).
The UT held that "parties who have been living together in a relationship akin to either a marriage or civil partnership which has subsisted for two years or more" does not require two years cohabitation, but two years subsistence of the relationship."
The phrasing of this specific paragraph of the Immigration Rules (352AA) for partners of a refugee contrasts with the requirements under Appendix FM of the Immigration Rules where 'partner' is specifically defined as "a person who has been living with the applicant in a relationship akin to a marriage or civil partnership for at least two years prior to the date of application" at paragraph GEN 1.2(iv).
This means that where the Immigration Rules are phrased to require (1) a relationship of more than two years duration; and (2) living together in that relationship - such as those applying under family reunion and certain applications under the 'old' family migration rules (Part 8) - a couple who have not lived together for a full two year period may be able to meet the requirements of the Immigration Rules with a shorter period of cohabitation. Please note, however, that to be successful the applicant will then have to go on and prove that the relationship has been subsisting for more than two years, which is a separate argument to be made.
It is important to note that this argument cannot be made in applications for partners under Appendix FM of the Immigration Rules (i.e. for partners of British citizens or those with settled status), because of paragraph GEN 1.2.(iv) and those applicants will still need to show that they have actually lived together for a minimum of two years.
The case can be read in full at: http://www.bailii.org/uk/cases/UKUT/IAC/2014/_UKUT_267_iac.html.
If you would like advice on whether this may have an impact on your immigration application, or if have any other queries then please do not hesitate to contact a member of our Immigration Team.