I don't know if this is true for mortgages as well but I believe that's how it works for credit cards. Once your credit is approved, the bank is not obligated to check it again unless you give them a reason to. It's on your to tell them your income has changed, but if you don't tell them, they don't have to actively check you. And obviously they don't actually want to know so they try their best to NOT know. (Yes it's screwed up...) but if you tell them, then they are obligated to check and change your credit limit. I think this may not apply for mortgages though, am happy to make a call tomorrow to my mortgage bank and ask to see what they say, am curious to know also!