Self employed
You have the option to reduce your Schedule C other income/sales by the amount from Form 1099-K that represents actual sales. Then enter the 1099-K under the income topic for Schedule C (there is a dedicated page for this form) and check the box to adjust the amount by the sales tax. (See screenshot below - click to enlarge.)
The net reported for 1099-K (on Sch C Line 1d - see screenshot) should match the amount you deducted from your sales income. These steps will avoid duplicating the income on the 1099-K.
