Ontario TMI & Additional Rent increase calculator

Did your TMI (Taxes, Maintenance, Insurance), also called Additional Rent or Operating Costs, jump this year? Enter last year’s and this year’s monthly figure below to see how your increase compares to inflation, then check the line items for free.

There’s no "you're fine" result: even a small increase can hide mis-allocated costs, excluded items, or double-billing. Every statement is worth a look.

Can my landlord increase TMI in Ontario?

Short answer: yes, and there is no legal cap on how much commercial TMI can rise year to year. Ontario’s rent-increase guideline applies to residential tenancies only; commercial Additional Rent is governed by your lease, not by a provincial ceiling. That is exactly why the size of the increase alone tells you very little. What matters is whether each charge is allowed by your lease and calculated correctly.

So what is a “normal” increase?

There is no official number, but a useful reference is inflation. When your TMI rises roughly in line with inflation (about 3% a year), the total is at least plausible on its face. When it runs several times inflation, something specific drove it (a reassessment, a capital project, a new line item), and that something is worth confirming against your lease. Either way, the increase is a prompt to look, not a verdict on its own.

The errors that hide inside a TMI increase

Most overcharges are not about the headline percentage; they are buried in the make-up of the bill:

• Excluded costs billed anyway: capital replacements, leasing commissions, or the landlord’s own overhead that your lease keeps out of the pool.
• The wrong share: a proportionate-share percentage that doesn’t match your lease, or vacancy costs shifted onto you.
• Management/admin fees stacked on the wrong cost base, or a fee taken on taxes and insurance.
• Estimates never reconciled, a tax credit never passed through, or the same charge billed twice.

These show up at any increase level, which is why the calculator never returns a “you’re fine” result.

How to check your own statement (free)

Upload your lease and your reconciliation statement: the free check reads both, compares every charge to your lease terms (HST included), and flags what doesn’t reconcile: each item tied to the exact clause, with a calm request letter you can send your landlord. For the full background, see the Ontario TMI & Additional Rent guide and the Canada-wide Additional Rent audit guide.

Calculator FAQ

No. The residential rent-increase guideline does not apply to commercial Additional Rent. Your lease is what governs, so the check compares your bill to your lease rather than to a cap.

Yes. A small increase can still contain mis-allocated costs, excluded items, or double-billing. The size of the change and the correctness of the bill are two different questions.

TMI Proof is software that checks your lease and statement; it is not a law firm and nothing here is legal or tax advice. Figures and rules are general. Your lease and Ontario law govern.