I don't have my 1098 from my mortgage company, tax deadline is tomorrow, 4/15/24, can I file an extension until I contact the mortgage company in the morning

Yes.

You can print and mail Form 4868 to file for extension or use this link to file it online.

Remember that this allows you until October 15th to file your return and you will not get a late filing penalty, HOWEVER, if you owe tax, you’ll still be charged interest and a late payment penalty. So if you’ll owe, get a payment in with the extension. 

For Desktop Users, type  extend   and click the “jump to” link for filing for extension.

Be sure to print and mail that Form before the original due date (April 15th 2024 for most of us) 

It is possible to file the extension with an online account and then finish and file using Desktop.