Box 18 – Employee's EI premiums = How much was deducted from your pay for employment insurance (EI) premiums.

Box 24 – EI insurable earnings = How much of your income is used to calculate what you pay for EI premiums. This should be much higher than Box 18. 

ex: If your Box 24 was $1000, you should only have about $16.40 in Box 18.

If the number in the boxes are incorrect on your actual T4 slip, then you should contact your employer to get a corrected slip.