"What happens if you dont file a W-2"
If you got a 2020 W-2 but did not file a 2020 tax return, the IRS will eventually calculate what they think should have been on your tax return, based on the information that they have. If it looks like you would have gotten a refund they will leave you alone (and you will not get the refund). If it looks like you would have owed tax, they will bill you for the amount of tax that they think you owe, plus penalties and interest.
