What is TMI / Additional Rent in a commercial lease?

TMI (Taxes, Maintenance, Insurance) — also called Additional Rent or Operating Costs — is a commercial tenant's proportionate share of a building's operating costs, reconciled each year against the lease.

How do I know if my Ontario TMI reconciliation is overcharged?

Common overcharges: capital projects billed as operating costs, management fees on the wrong base, gross-up applied to fixed costs like taxes, and HST errors. CAM Proof checks each line against your lease.

Is the TMI check free?

Yes — the first check is free. Upload your lease and TMI / Additional Rent statement and CAM Proof flags what doesn't reconcile, each finding tied to the exact lease clause.

For Ontario commercial tenants

Is your TMI bill correct?

Your year-end TMI / Additional Rent (Taxes, Maintenance, Insurance) is one of the most over-billed lines in a commercial lease. Upload your lease and statement — we check every charge against your lease terms, HST included, and flag what doesn’t reconcile. Every flag cites the exact clause.

Not a fight with your landlord — a calm CRA-compliance reconciliation. Additional Rent carries 13% HST, so getting it right keeps your input-tax-credit filing clean.

Check my TMI, free →See a worked sample — $6,185 flagged →

Free checkNo accountEvery finding cites your lease clause

A worked example

See exactly what you’d get

A sample Ontario plaza reconciliation, run through the check — the findings, then a ready-to-send letter. This is a demo, not your bill.

ExampleA sample Ontario plaza reconciliation — not your bill. Your own check runs on your lease.

What the check flagseach item cites the lease clause

Parking-lot repaving (capital project) doesn't belong on the bill

Your lease excludes it (Sec 7.2(a) (capital excluded)) — it isn't a shared cost the tenant owes, so take it off.

R20 · Ironclad · Lease Sec 7.2(a) (capital excluded)

$6,000.00

over-billed

HST over-charged on your TMI

HST should be 13% of the net additional rent ($18,500.00) = $2,405.00, but the statement shows $2,590.00 — a $185.00 over-charge to correct.

R26 · Ironclad · Lease GST/HST on additional rent (CRA, Excise Tax Act)

$185.00

over-billed

Amounts shown are building-level pool figures; what lands on your bill is your proportionate share of the pool — but a wrongly-included item (like the capital repaving above) inflates every tenant’s share until it’s removed.

Your reconciliation request (draft)

Draft · review with your accountant before sending

July 22, 2026

To: [Your landlord / property manager]
From: [You, tenant]

Re: Sample Ontario plaza TMI 2025 (illustrative): request to reconcile Additional Rent (TMI)

In reconciling my year-end Additional Rent (TMI) statement against the lease for my records, a few items don’t appear to reconcile. Because Additional Rent carries HST, these affect my input-tax-credit filing and the records I’m required to keep for CRA, so I’d like to line them up before I close my books:

Parking-lot repaving (capital project) doesn't belong on the bill, $6,000.00 (Lease Sec 7.2(a) (capital excluded))
HST over-charged on your TMI, $185.00 (Lease GST/HST on additional rent (CRA, Excise Tax Act))

Total in question: $6,185.00.
Could you please send the supporting invoices for these items and, where warranted, a corrected statement, so my HST filing reconciles. Each item notes the lease section it relies on. Thanks very much, happy to hop on a call.

Regards,
[You]

We don’t invent overcharges

Every flag cites the exact lease clause it turns on — so your request to the landlord is grounded, not a guess.

Reproducible to the cent

Calculated deterministically from your statement and lease, HST included — re-run it and the numbers match.

Check my own TMI, free →

New to TMI? Read the Ontario TMI & Additional Rent guide — what it is, the overcharges to watch for, and your rights as a tenant.

A starting point for review, not legal, accounting, or tax advice. Confirm each item against your lease and with your accountant before acting. Sample figures are illustrative.