How do I get 1099 form for retirement withdrawals?

Yes, you can file without it.

You should contact the plan administrator. There will be information on the official 1099-R that you might not have access to. If you absolutely can't get it, you can file a substitute.

Substitute 1099-R

If your plan administrator doesn't give you Form 1099-R for 2020 (or the one you receive is wrong and your plan administrator refuses to correct it), do your best to obtain the form or correction before completing a substitute on Form 4852.

You'll be required to:

 - describe your communications with the plan administrator in your attempt to get the form, and

 - attest to the IRS that you were unable to obtain it.

Complete a Form 1099-R as if you actually received the correct form. Enter as much information about the payer as you can, including name, address, and the amounts for 2020. Then complete the information for the substitute form.

Type 4852 in the search box then select the Form 4852 form and click Open Form button. Follow the directions at the top of the page for entering the 1099 R information.  See screenshot below.