When a condo owner does not pay monthly fees can the association collect late fees or interest?

Yes, generally. Your governing documents could be very specific on this issue.

(Generally, assessments are levied against owners in order to pay the operating expenses of the community. Often, not only do owners agree to pay them when they purchase a unit, but your governing documents may indicate that the liability to pay is also a personal liability.)

It's a good idea for the association's treasurer to set the late fee amount and the due date and remind owners annually. Often these details are included in assessment payment book coupons.

Interest is also chargeable, but only according to the amounts documented in the CC&Rs.

Finally, depending on the expenses that the assessments pay monthly, the association may deny services to a non-paying owner, to and including utilities, club room or pool access, and so forth. As a last resort, the association may be able to sell the unit to retire the debt.