In the sense that they should be providing you with a W-2 it could be considered not legal. However, the difference to you is probably not material, and the IRS isn't going to get excited about one Form W-2.
Form 8919 is used to report wage income that was incorrectly reported on Form 1099 or not reported. It will require you to pay FICA and Medicare taxes on the payments (remember - you would have paid them anyway) but not the matching employer share. (Sometimes, the easiest solution is to just report it as self-employment income and pay self-employment tax on it. Even if reported as wages, you would still also have to pay the employee’s portion of social security and Medicare.)
If you choose to report as wages, and if this is a bonus, car allowance or other amounts paid to you on Form 1099 and you already receive a Form W-2 from your company, you should use Reason Code H. Reason Code H is "I received a Form W-2 and a Form 1099-MISC from this firm for 2012. The amount on Form 1099-MISC should have been included as wages on Form W-2." If you use Reason Code H, a Form SS- is not required.
Form 8919's "Who Must File" instructions include:
You must file Form 8919 if all of the following apply.
• You performed services for a firm.
• The firm did not withhold your share of social security and Medicare taxes from your pay.
• You believe your pay from the firm was not for services as an independent contractor.
• One of the reasons listed below under Reason codes applies to you.
Reason Code H is "I received a Form W-2 and a Form 1099-MISC from this firm for 2015. The amount on Form 1099-MISC should have been included as wages on Form W-2"
