There is no statutory basis for disqualifying (or qualifying for that matter) an applicant based upon time spent in or out of the UK. The rules for ILR at the end of the 2 year probationary period are spelled out in Paragraph 287 and they say nothing about how much time the applicant needs to be in the UK.
What they do say, however, is that the marriage must be subsisting and that both parties intend to live together permanently. That's what the law says, and the law-makers were silent on what the definition of 'subsisting marriage' is.
In answering that, the policy side has a framework for determining whether or not a marriage is subsisting, and it includes things like having 10 pieces of correspondence for each of the two years and so on. We get lots of threads about that part.
They also look at time spent in and out of the UK. And because it is not part of the 'official rules', they put guidelines in the 'unofficial rules', a portion of which is properly known as the IDI's.
The IDI's tell us that the applicant and sponsor should have spent the majority of the 2 years living together. And if this is not the case, then they need to have a good reason for the application to succeed. So the majority of time means at least 1 year together in the UK.
In 2004, I was approached by a Russian woman whose ILR application had failed because she was out of the UK for 110 days and her refusal letter cited an unpublished rule stating 90 days as the maximum. I had never heard of it, and requested it under the Freedom of Information Act, but my request was refused, so I appealed and I lost the appeal. Sometimes things happen like that.
And here in UKY last year, a staff member at the British Consulate in Los Angeles sent an email to a forum member (PhoenixMoon, for those that recall her) that said since she was out of the UK for more than 90 days, that her entry clearance had been revoked. That was total bollux, and I complained and they ultimately retracted. But they never cited their source.
Those incidents are enough to indicate that there's something that says 90 days, but it's hard to find out exactly where. I have it in mind that since the fee increase was so wildly dramatic, that public interest has tipped in my favour and we actually need to see it because so much money is at stake for each applicant.
On a separate strand: I was looking at the new IDI's last week when the new BIA went live and noticed that sections of Chapter 8 (Family) have gone completely and mysteriously missing. Thankfully, an unsung hero in the Advocacy Group is going to make enquiries about the missing sections with a view towards a Freedom of Information Act request. Stay tuned.