[Updated 2/10/2025]
See these pages for the meaning of the codes in box 12
H&R Block: What the Form W-2 Box 12 Codes Mean | H&R Block (hrblock.com)
Intuit: What do the letter codes in box 12 of my W-2 mean? (intuit.com)
Box 14 is used by employers to report "other information." The codes are created by the employer so you may have to contact your HR department to discover their meaning. Also, ask if they know which of them must be included on your tax return.
See these help pages regarding box 14.
The information that your employer lists in Box 14 of you... (intuit.com)
The code for my W-2 (Box 14) is not listed. What do I enter? – Support (taxslayer.com)
The code explanations might not inform you whether the amounts reported on your W-2 in box 14 need to be reported on your federal tax return.
When using Sprintax, the box 14 entries may result in a pop-up box telling you that the preparation of your tax return may require extra work and result in higher charge.
If you come to the conclusion that an amount in box 14 is not required to be on your tax return, you could omit that amounts when entering your W-2 information into Sprintax and see if their omission permits you to proceed.