Do you report online sales (Poshmark /eBay) if total Gross is less than $400 ?

[JamesG1]

It all depends.  Do you have other income to report or is this the only income that you have to report?

US citizens and resident aliens are subject to tax on worldwide income from all sources and must report all taxable income and pay taxes according to the Internal Revenue Code.  IRS Publication 17, page 2 states:

You must report all income on your tax return unless excluded by law, whether you received the income electronically or not, and whether you received a Form 1099-K   or not. 

The box 1a and other amounts reported on Form 1099-K are additional pieces of information to help determine the correct amounts to report on your return.

However, if the online sales is the only income that you have to report, you are required to file IRS Form 1040 and Schedule SE IRS Form 1040 Self-Employment Tax, if your net earnings from self-employment was $400 or more.