Immigrationboards.com

Hello and congratulations on providing this much-needed service.
I obtained LL to enter in 2014 and have just obtained LL to remain, expiring late in 2019. I'm a U.S. citizen married to a UK citizen. My approval letter states I would need to apply and qualify for ILR on a different basis if my relationship breaks down. It referred me to the UK visas website, with no further instruction. I've looked through the website/immigration rules and can't find anything addressing this situation. Any thoughts on where I can find these rules, in case that becomes my situation?

It means you would have to find an alternative visa you qualify for and apply for it then wait the required period for ILR.

If your current relationship breaks down, you cannot apply for ILR based on your marriage to a UK citizen.

Unless there is domestic violence and substantial documented evidence of this, ILR will not be possible on your current visa is your marriage breaks down.