Funny, I would think exactly the contrary if the mortgage bank had my money and investments too.
They might freeze my accounts or liquidate my investments so that the mortgage is reduced to meet the affordability criteria or whatnot.
Maybe as a multi millionaire with a mortgage 10% the value of one’s investments, in which case who would care about telling them or not telling them about working or not working anyways 
Seriously how would a landlord know and care about that if you pay?
The bank lending you money is managing a risk and if this risk is monitored with salary account cash flows and source of cash (employer), you could be asked.
I don’t see a similar case as landlord and currently renting, if you’re paying in due course. Of course, if you happen to be looking for a new apartment, you’d have to have a good record and/or network to be considered top of the list with an atypical situation.
If it’s not pledged in the contract, they can’t.
Again, it’s not in their interest to break your finances, end a mortgage, liquidate your assets… but if there’s a “problem”, even something atypical they detect as a risk, because it doesn’t fit their pattern and/or their compliance and/or the initial commitment, you’ll be asked to solve the problem.
Then, if you have a 1M mortgage with real estate, and 10M liquid assets aside, they’d be hurt more than you would if you decide to pull the trigger and move away. Not sure in that case you’d get questioned if no salary comes in.
Like with any partner, it’s a balance sheet issue.
murphys law says he doesnt need to know. He might cancel due to renovations/ self use/etcetc
It wanted to point out, that an alternated income situation can also affect your housing situation - by not getting a new lease because competitors have better paychecks.
I realized just now, that if I leave my job, the banks will find out anyway, as at some point I would have to change my 2nd pillar pension fund to an alternate solution.
ah, you pledged your 2nd pillar? yeah. then they will anyway know quite quickly. in which case you better talk with them first to see what they say and decide what to do based on their answer.
Sounds like a US thing. I would be surprised if Swiss banks were allowed to do this at large scale.
I agree with the all the rest of your assessment.
It’s very much a thing, and actually can be decent investment on the other side.
I believe we were never asked to provide any proof over the last 11 years and 2 mortgage providers. The mortgage was renewed multiple times.
Current account in different bank so they have very little visibility.
For renewal one of the biggest advantage for current provider must be that there is no paperwork requirements 
If there would be a downward market repricing they would maybe be required to ask?
Renewal only occurs if you have a fixed mortgage, correct? For SARON you can basically go ahead longer times without triggering any checks…
SARON can often have a limit too e.g. SARON + 0.7% for 3 years. After which this mortgage needs to be re-financed.
What is often? 10%, 30%, 70% of all Saron mortgages?
Yes.
Could you confirm what this means exactly? Does this mean that you don’t need to pass or provide proof of passing affordability criteria if continuing the mortgage with the same provider?
Indeed. They never asked to see up to date tax declarations nor salary slips when we renewed. Just an offer letter with new conditions that needed to be signed. Fixed two year contracts and saron 3 years.
Obviously doesn’t mean it won’t happen in the future or elsewhere.
how long was it between original mortgage and renewal? mine was 10 years and UBS wanted to see everything again.
I think we’re approaching 7 years with current provider so they might want to check closer every 10 years and maybe in particular when you reach official retirement age.
I found out, unofficially, from a BIG bank representative, that in case of unlimited SARON mortgages, there are no actual checks regarding income, as long as the mortgage is paid. For mortgages that have a fixed term, including SARON, sometimes they might check again the income and look more closely at your situation.
This doesn’t change the fact that, in case your financial situation changes, you should inform them, in case that this is specified in the contract you have with them.
What I can say is that my 10 years fixed mortgage is almost up and the bank never asked anything (my salary has been going to a different bank for the last 5-6 years).
This is a tough spot to be in. In my experience looking at the Swiss market, banks are mostly focused on managing their risk.
The Loan to Value (LTV Factor): Assuming your apartment in Zurich has appreciated (as many have over the last few years), your actual Loan-to-Value (LTV) might be lower now. If it has dropped toward that 66.7% mark (the 1st Tranche), the bank generally has less reason to worry, since the ‘riskier’ 2nd tranche is smaller or gone. Again this is my experience.
A Visual Guide: I actually put together a small visual guide (chhyporechner.com) because I found the bank’s math hard to visualize. It’s just a mathematical simulator I made for my own house hunt—not financial advice—but it gives a quick overview of how the 1st and 2nd tranches split.
The ‘What-If’: You could plug in your current estimated value to see if you’ve moved more into that ‘Green Zone’ (1st rank). It might help you visualize your safety buffer before making the leap.
It’s a free project, no ads or login required, just meant as a preparation tool.