TMI / CAM & Additional Rent: What Commercial Tenants Actually Pay
You understand the net rent. What blows up a commercial tenant’s budget is the additional-rent line called TMI — billed on an estimate, then trued up at year-end.
What is TMI / additional rent in a commercial lease?
TMI stands for Taxes, Maintenance, and Insurance — operating costs charged on top of the net rent, collectively called “additional rent.” The landlord usually bills an estimate monthly alongside the net rent, then reconciles to actual operating costs at year-end: if actuals exceed the estimate, the tenant tops up; if they’re lower, the tenant gets a credit. CAM (Common Area Maintenance) is a common name for the maintenance portion. Additional rent also attracts 13% HST.
Source: Ontario commercial leasing practice / OREA commercial clauses (2026)
I’m Arthur Zhao. The place commercial tenants get burned isn’t the net rent — it’s TMI. Net rent is written into the lease, clear as day. TMI is an “estimate” that changes at year-end, and what it includes and how it’s allocated is exactly what most tenants skim past at signing. Then a “year-end reconciliation — please remit $8,000” bill lands, and they realize they signed a blank cheque. Here’s how TMI works and where you can negotiate.
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How TMI is billed monthly
⚠️A landlord’s TMI estimate at signing is often set low — it makes the deal look more competitive, and the year-end reconciliation makes up the difference. The fix: ask for two or three years of actual TMI history, not just this year’s estimate. A big gap between the estimate and the historical actuals is a red flag.
The year-end reconciliation — top-up or credit
Three defences every tenant should negotiate
💡 The items most often hiding in TMI that shouldn’t be there: the landlord’s own mortgage interest, leasing commissions, marketing to attract new tenants, and capital-nature major repairs. Before signing, ask line by line what additional rent includes and excludes, and get an exclusions list in writing — far cheaper than fighting about it later.
Why this line is worth your time
In many Ontario retail and industrial properties, TMI is 30–50% of the all-in occupancy cost. Which means shaving a dollar off net rent can matter less than winning a reasonable cap and exclusions on TMI. When you negotiate a commercial lease, move half the energy you’d spend beating down net rent onto managing TMI — it usually pays better.
Frequently Asked Questions
Is TMI fixed, or does it rise every year?
TMI is not fixed. It tracks actual operating costs each year: tax reassessments, rising premiums, and pricier maintenance all push it up. There’s also a year-end reconciliation, so if actuals beat the estimate you top up. Negotiate a cap on controllable costs and ask for history to read the trend.
Do I have to pay a year-end reconciliation top-up bill?
If the lease allows reconciliation to actual costs and the bill is within the lease terms, usually yes. But if the lease gave you audit rights, you can review the landlord’s cost detail for items that shouldn’t be charged to tenants or that are capital repairs. That’s exactly why you negotiate audit rights at signing.
Can a capital repair like a new roof be charged to my TMI?
Ideally, no. Roof replacement, structure, and full HVAC replacement are the landlord’s capital expenditures, not day-to-day operating maintenance. Tenants should expressly exclude capital-nature items from TMI at signing, or they may be allocated into your additional rent.
TMI or net rent — which should I focus on when negotiating?
Both, but don’t neglect TMI — it’s often 30–50% of all-in cost. A dollar off net rent frequently matters less than winning a controllable-cost cap, capex exclusions, and audit rights on TMI. Put half your energy into the TMI clauses.
Does additional rent attract HST?
Yes. Net rent and TMI additional rent are both commercial rent and both attract 13% HST. Don’t miss it when budgeting: all-in monthly ≈ (net rent + TMI) × 1.13.
Arthur Zhao
Real Estate Broker · FRI · ABR · SRS · PSA · MCNE · E-PRO · CLHMS & GUILD Elite · REAIS
VP & Branch Manager, Bay Street Group Inc.
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