1099-NEC that report WRONG income

there is no tax advantage to the employer to give the wrong amount.

You are paying the SE tax.

ask the employer for a corrected 1099-NEC.

@TheWisdom 

maybe you misplaced a paycheck and did not deposit it.

@TheWisdom 

If you received an erroneous 1099, You have several choices (I would do #3):

1. Ideally, you get a corrected 1099-NEC from the payer
2. Report only the correct  amount.  Attach a copy of the 1099 and a statement explaining the circumstances. You can't e-file. From the IRS instructions for form 1099-Misc: Form 1099-MISC incorrect? If this form is incorrect or has been issued in error, contact the payer. If you cannot get this form corrected, attach an explanation to your tax return and report your income correctly.
3. Report all  the Income, on the 1099-NEC, on schedule C and take a deduction for the difference, under other expenses, call it something like "adjustment for erroneous 1099-NEC "
4.  Report only the correct amount and hope you can explain it away when & if the IRS contacts you

Maybe they included some expenses they reimbursed you for?

Thanks, Hal_Al.

I see the #3 solution is optimal tho. Are there any cons (weaknesses) of the #3 solution I should know about?

Keep your records, in case you get audited.  It may be helpful if you can show that you made some effort to get a corrected 1099-NEC. 

That said, #3 is the most recommended action, in this forum. 

Thanks, mate!