How is income determined to be taxable before a Form 1099-K is issued?

[Patrice1986]

I'd like to know if there is a way in which income is determined to be taxable before it is reported on Form 1009-K.  I ask because many people use payment apps to transfer money for many different reasons outside of side gig or business related transactions (ex: to send a family member a birthday gift).  Will you automatically receive a Form 1099-K if you meet the income threshold and even if the income is non-business related?

[Connie C]

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!!

[Lizy0312]

I have a question similar to this.  I am a tennis coach and have started teaching at a second location where individuals pay through Venmo.  What is the threshold for reporting and what is the best way to document this?

Thanks!