"Code K is 20% excise tax on excess golden parachute payments." <== Box 12

"K – 20% excise tax on excess golden parachute payments. Include this tax on Form 1040 Schedule 2, line 17k, enter the total amount of the tax"

https://www.hrblock.com/tax-center/irs/forms/understanding-form-w2-box-12-codes/

K = Pre-tax dental and vision deductions <== Box 14

"Since there’s no standard list of W-2 codes for box 14, employers can list any description they choose. If the code is unclear, contact your employer and ask what the internal revenue code represents."

https://www.hrblock.com/tax-center/irs/forms/understanding-w-2-boxes-and-codes/

https://support.taxslayer.com/hc/en-us/articles/360015701832-What-are-W-2-Box-14-Codes-for-Defense-F...

Box 12 is more like required reporting and Box 14 is Informational reporting. Typically, that's because Box 12 will impact Gross vs Net and tax withholding. Box 14 is "provided for you information, because you might need to use or refer to it elsewhere."