Rental Increase Letter

[ToRena Webb-Thomas]

I have a tenant I inherited in Dec 2015. I was told their rent included parking and storage in the basement. I wasn't given any copy of the lease and he wouldn't sign a new lease or TAW agreement for our Property Management. I want to raise the rent because they are paying the least for the biggest unit, a storage room in the basement and parking. No other tenants have access to the basement. Rent hasn't been raised since I purchased in 2015 and I'm sure for some time before that. Do I list in the Rental Increase letter "All terms from the previous rental agreement will remain in effect" if I have never seen such lease or terms? I want to send out the letter now for rental increase as of Jan1. Are there any other clauses to include? Thoughts?