I received a W-2C from my employer regarding tax year 2020. Noting incorrect amount of social security withheld on original W2, actual is an increase amount of $1656.74

[SteamTrain]

For most people, for that particular change, there is nothing you need to do, since it usually doesn't affect your income taxes at all.

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The BUT is this.  IF you worked for more than one employer in 2020, and IF the total $$ withheld for SS in box 4 of the different employer W-2 forms adds up to more than 8537.40, then you could file an amended tax return for 2020, and get a refund of the excess SS withheld that was over 8537.40.  (if married, this only applies to your own W-2 forms. Each spouse's W-2 forms are considered separately)

[Opus 17]

If box 1, box 2, box 16 or box 17 didn't change, then you generally don't need to do anything.  This is a result of the temporary suspension of social security taxes during the pandemic.  Your employer caught up on those suspended taxes, and has to issue a corrected W-2 to show the final amount collected.  It doesn't change your income tax return and you don't need to file an amended return.

The only time you might need to file a return is if you worked for more than one employer and your total wages were more than $132,900.  In that case, the catch-up withholding and adjustments might have resulted in you paying too much social security (FICA) tax, as described above.