what is earned income for self employed who receive social security benefits

I am planning to receive social security benefits and trying to understand what I can early as contractor while receiving these benefits, and what the IRS reports to social security as earned income.

I have spoken to Social Security people and they do not know.  Many times I have tried to speak to one who does.  They claim I have to send some form  to them monthly showing income and I cannot locate info on this anywhere.

I know the threshold is 1950 per month.  Or that x 12 for year.... 


If my net is within the threshold, the Social  Security told me that is irrelevant and there is some forumula the IRS uses that I need to understand?  That does not have to do with my net earned income...  And also some monthly formula?- which makes no sense as one month I have maybe a lot to set up new work, and anotheris less....

Regardless if I am not complicating this with any other moneys... how do I know what my net is monthy and yearly to not go over and if I do go over, how do I know what and when will happen?

Taxes are reported annually, 1099s 1 x year so I don't understand how this all happens also.


Thank you.