Well, one of the requirements for ILR (permanent residency) is that you have to show proof that you have lived together for the entire 2 years of the spousal visa.
You do this by providing 6 letters/documents, addressed to both of you at the same address, evenly spaced over the 2 years (i.e. one document for each 3-month period). The letters must either be addressed to both of you jointly or you can send 6 letters each, addressed to you individually.
If at any time during the 2-year period you have not lived together, you must explain your reasons why, and how you have maintained contact while apart, and you should provide any supporting evidence (for example, if one of you had to work abroad for a while, you would provide evidence of this from your employer).
Here's what the notes from the SET(M) application form for ILR say:
Note 8 We need 6 letters or other documents addressed to you jointly or in both your names. If you do not have enough items in your joint names, you may also provide items addressed to each of you individually if they show the same address for both of you. Examples of acceptable letters and documents are listed below. They must be originals.
The dates of the letters or documents should spread over the whole 2 years. They should be from at least 3 different sources.
Please give an explanation on a separate sheet if you cannot provide 6 items; if the documents are not addressed to both of you; or if they do not cover the 2-year period. If you and your partner lived with relatives or friends for some or all of the 2-year period, please provide a letter from the relative(s) and/or friend(s) confirming this.
If you did not live together for any part of the 2-year period, tell us the reasons for this and whether you stayed in contact with each other during this time, and provide any relevant supporting evidence.
Examples of acceptable types of letters and documents:
- letters or other documents from government departments or agencies, for example HM Revenue and Customs, Dept for Work and Pensions, DVLA and TV Licensing
letters or other documents from your GP, a hospital or other local health service about medical treatments, appointments, home visits or other medical matters
- bank statements/letters
- building society savings books/letters council tax bills or statements
- electricity and/or gas bills or statements
- water rates bills or statements mortgage statements/agreement tenancy agreement(s)
- telephone bills or statements