Copy and pasted from the website (and the link to the site)
A tenant is responsible to pay the landlord the full rent on the day the rent is due. If the rent is not paid on time, the landlord may charge the tenant a late payment fee.
A landlord must tell a tenant in writing that they will charge a late payment fee if the tenant doesn’t pay rent on time. A landlord can include this information:
•on a tenancy agreement; or
•in the house rules.
Once a tenant knows about the fee, a landlord is entitled to charge it.
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The rate for a late payment fee is set by regulation. A landlord cannot charge more than what has been set by regulation. A landlord may charge a late payment fee of:
•up to $10.00 for the day the rent was due; and
•up to $2.00 for each day after the due date that the rent is late in any consecutive number of rental payment periods, to a maximum of $100.00.
When a landlord charges a late payment fee, the tenant must pay the daily rate:
•up to and including the day they actually pay the rent in full; or
•the fee reaches the $100.00 maximum.
http://www.gov.mb.ca/cca/rtb/ot/gbook/s2tenagree_latepaymentfees4.html