Switching employers mid-year often results in a overpaying withheld social security taxes.
For tax year 2021, once an employee earns $142,800 from an employer, social security taxes are no longer withheld. This results in a max social security tax withheld from pay of $8,853.60. If a taxpayer works more than one job and combined wages exceed $142,800 from multiple employers in 2021, then more than the max social security withheld tax limit per individual, $8,853.60, will be withheld for the taxpayer. However, this excess withholding amount is not lost, but will count as additional withheld federal taxes paid for the year. A taxpayer will receive this tax credit when filing their personal tax return for that calendar year.
Keep in mind that knowing that the max withheld social security tax has been reached at one employer in the year does not allow a taxpayer to request the second employer to stop withholding social security taxes from their pay at the new job. Each employer acts independently and assumes that they are your only employer in the year with regard to withholding social security taxes from your pay.