I tell my clients this everyone year. However I always get one that says “So and So did it last year” well here is what the IRS says about it:
Authorized IRS e-file Providers are prohibited from submitting electronic returns to the IRS prior to the receipt of all Forms W-2, W-2G, and 1099-R from the taxpayer.
If the taxpayer is unable to secure and provide a correct Form W-2, W-2G, or 1099-R, the return may be electronically filed after Form 4852 is completed in accordance with the use of that form. This is the only time information from Pay stubs or Leave and Earning Statements (LES) is allowed.
For further information see Publication 1345 Chapter3 ” Submitting the Electronic Return to the IRS” and Chapter 6 ” IRS e-file Rules and Requirements”.