Liability Insurance is different from professional or union dues.
Membership in a professional body or college may or may not include liability insurance in some form.
Usually, deductible items appear in box 44 of a T4, or through membership receipts.
If you are asking about an insurance policy, this might be deductible as an expense if you were filing a business return, but would not qualify for a personal deduction from income as professional fees or union dues.
The only personal qualifying non-business insurance that provides a tax credit is private Medical insurance premiums.