Your filing of the form 4868, along with any additional tax payment, if there are any, gives you until Oct 15, 2022, to file your return for 2021. In your case you stated you expect a refund for your overpayment. If you were to find for any reason an error on your tax preparation work, and owe money, send in the payment as soon as possible to stop the clock on any penalties. File as soon as you get the missing information before Oct. 15, 2022, and all will be good!
