Proceeds from sale of company

Hi,

 

I worked for a startup that was sold to Experian. I received a payout in three payments that was a % of the sale price of the company  (not a huge amount). The first payment came from the company I worked for after the sale closed. Payments 2 and 3 came from Experian. Experian sent me a 1099-misc for the payments they made.

Is this considered income subject to self employment tax? I was not working for either company when the payments were made.

 

Thank you!!