Self employed

I want to tag on to this question a bit...
I understand as an LLC (online coaching/teaching business) - I will need to file estimated taxes quarterly. Form 1099-K is only issued at the end of the year, right??

 

?? How do I estimate (guess-timate) the taxes to be paid each quarter? My sales has peaks and valleys, depending on when I promote my courses. 

 

Thanks for sharing your time and expertise. 

You ROCK!!