1st Step: Determine your Cost Basis.(Speak to your Accountant)
Once that has been established you can see what your Capital Gain exposure will be.
2nd: As stated below, there are 4 Seller Assurances you must approve on a 1099 that will exempt you from any gain tax.
Please consult Page 2 of a 1099 From to see what applies to your situation.
Feel free to call me with any questions.
Best of Luck