letter confirming permanency, salary, etc

I don't want my boss to know that I 'm applying for a mortgage but I need a letter confirming I'm permanent, salary, etc. I was gonna tell him I'm reorganising a personal loan, but I wouldn't even want him knowing that. Any alternative reason I can give that doesn't involve a mortgage app?

Do you have a contract that has permanent written on it?

At some point they will want a salary certificate signed by your employer if you apply for a mortgage. I not sure if they need it to give you an offer or if theyll want it before you go ahead with the mortgage

@AOR its virtually certain the Bank will want it - is he the only one that signs these? Must be a small company and he will find out anyway. Or else ask somebody in Finance to do it.
What makes you concerned? (S)he might be delighted that your sticking down roots.
[At the moment most employers are more concerned about surviving that having time to be concerned about your housing plans.]