In 2017, my wages maxed out FICA, however separately I had $10k of consulting income (1099).

[VAtaxman]

Do I need to send SSA the employer portion of that $10k. Is there a specific tax form I need complete for this self-employment income or just 2017 1040. 

[Critter]

When you complete the Sch C section of the program it will automatically compute the SE taxes you owe taking into consideration the SS tax cap that you hit and the tax will be added to your federal income tax bill on the form 1040. 

[dmertz]

... and since you already maxed out FICA at your W-2 employer, the result on Schedule SE will be that you owe no Social Security taxes on your self-employment income, only the 2.9% Medicare taxes.