With regards to late rental payments, we usually suggest that once you have served the tenant with at least seven or eight N4’s then you can issue a notice of termination based on persistent late payment of rent which is a Form N8. This notice must be 60 days’ notice terminating on the last day of the rental period. Once you have issued the notice, you may apply to the Landlord and Tenant Board anytime within the 60 day period if you think the tenant will not leave according to the notice. To apply to the Board you will need to file the L2 Application along with a Certificate of Service. All the forms can be obtained from the Board’s website at https://tribunalsontario.ca/ltb/forms/.
You should also search through Board decisions posted to CanLII, https://www.canlii.org/en/on/onltb/, for dealing late payment of rent cases to get an idea on how the Board deals with this issue.