Many bylaws contain a provision for an owner vote if a special assessment exceeds a certain dollar amount, or is greater than a multiple of an owner's current assessment. They may state, for example, that if a special assessment is greater than $300 or five times an owner's current monthly assessment, a vote of 2/3 of the owners is necessary to pass it.
Per the IL Condo Act, such limitations cannot be placed on expenses for the repair or replacement of the existing common elements. The expense must be related to an addition or improvement in order for the owner vote to apply.