The government already knows all that information about you. You give your family information to your employer which passes it on to the government. Your mortgage company (and any other financial institution for that matter) sends the government information about your loans/accounts. That’s how they know you filled out your taxes correctly to begin with.
You give your family information to your employer so they can estimate your taxes. But you’re not required to keep them up to date.
So for instance if you tell your employer that you’re single and then get married, you are not required to update your employer. Same is true of having a child, etc. Hence the need for an official annual update, which goes directly to the IRS.
The government already knows all that information about you. You give your family information to your employer which passes it on to the government. Your mortgage company (and any other financial institution for that matter) sends the government information about your loans/accounts. That’s how they know you filled out your taxes correctly to begin with.
You give your family information to your employer so they can estimate your taxes. But you’re not required to keep them up to date.
So for instance if you tell your employer that you’re single and then get married, you are not required to update your employer. Same is true of having a child, etc. Hence the need for an official annual update, which goes directly to the IRS.