You should be able to set a model action that updates the contact reference field to blank when the checkbox field is updated.

we have given it as action type: Update a field on row, model application field contact__c, value=  ;

Still this field giving contact id

How about action type “remove all rows from model” then requery the model. This would erase everything in the model, which may not be what you want.

thanks for ur help. its working fine. previous in that field i left it blank. now i am giving {{Blank}}. its working fine

when i add for value={{blank}}, for those field its working fine. but when i check on new borrower check box, existing data coming for model. this happen cause of “value={{blank}}”.

I’m not exactly clear on the sequence of events here, but it sounds like you are entering data into the model then toggling the check box off and on and seeing that that unsaved data is still showing up. You may have luck if you “remove all rows from model” as part of your action sequence. Another idea would be to have separate pages for existing borrowers and new borrowers with a button at the top of each that would redirect to one another. So if you click “existing borrower” button it would redirect or open a pop up to your “existing borrower page” and if you click “New Borrower” it will redirect or open a pop up to your New Borrower page".