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No, if there is no policy in place or clause in the lease that allows the landlord to charge late fees at the time they would be incurred, then the landlord can't implement a policy that imposes them for past activity. They can only be for future late payments once the change is implemented.
So if there is no policy in place when rent is late, then the landlord is out of luck for imposing them.
So if there is no mention of a late charge in my lease I do not have to pay it, is this correct?
That is entirely correct.