Most of the fight in a medical office lease is about base rent, because base rent is the number everyone can see. The number that actually determines what you pay in years two through ten is smaller, quieter, and buried in the operating-expense clause: the base year. It is a single setting — one line establishing a spending level — and it decides how much of the building’s rising costs get pushed onto you and how soon they start arriving. Get it wrong at signing and you inherit an escalating bill you cannot renegotiate until the lease is up.

This is a piece of the operating-expense clause worth pulling out and looking at on its own, because it is where landlords quietly recover money that never appears in the rent you thought you agreed to.

What a base year actually is

In a full-service or base-year lease, your rent is quoted with the building’s operating expenses — property taxes, insurance, common area maintenance (CAM), utilities, management fees — baked in for a single reference year. That year is your base year, usually the calendar year in which your lease starts. The expense level in the base year is your floor. You do not pay it separately; it is already inside your rent.

What you pay separately, going forward, is the increase over that floor. If the building’s operating expenses run higher next year than they did in the base year, you pay your proportionate share of the difference. The base year is the line the meter starts from.

That makes the base year one of the most consequential numbers in the document, and it is almost never negotiated as hard as it should be — because at signing it feels like a technicality, and its cost does not arrive until the first reconciliation lands, well over a year later.

How increases over base accrue

Here is the mechanism. Each year the landlord tallies the building’s actual operating expenses, subtracts the base-year amount, and bills you your pro-rata share of the increase — your rentable square footage as a percentage of the building’s. A small annual bump in the building’s real costs, applied to your slice, compounds quietly year over year.

Two features make this expensive in ways owners underestimate. First, it never resets. The base year stays fixed for the life of the lease, so in year eight you are paying the accumulated difference between today’s costs and a spending level from nearly a decade ago. Second, the further you get from the base year, the larger the gap — and the larger your bill — even if nothing about your suite has changed.

Where to push: the single most valuable move is to define the base year as the first full calendar year of your occupancy, not the year you sign or take possession. A base year that is even partly a stub — a few months of a partially built, partially occupied, partially billed building — understates true costs and sets your floor artificially low. Which is exactly the trap.

The low-base-year trap

This is the one that catches good tenants. A base year is only fair if it reflects the building running normally — fully occupied, fully assessed, fully operating. When it does not, your floor is set too low, and you start paying “increases” that are not really increases at all — they are the building simply reaching its normal run-rate.

Three situations produce an artificially low base year:

  • The building was under-occupied. Many operating costs scale with occupancy. A half-empty building spends less on utilities, staffing, and services. If your base year is a lease-up year, the building’s costs are understated — and as it fills, your “increases” are just normalization you get billed for.
  • The property had not yet been reassessed. Property taxes are often the largest single line in operating expenses. A building that recently traded, was newly built, or is between assessment cycles may carry a temporarily low tax figure in your base year. When the assessor catches up, the jump lands on you as an increase over base.
  • The expense figure itself is soft — one-time credits, deferred maintenance, or an unusually mild year that will not repeat.

The failure mode is the same in all three: you negotiate hard on base rent, feel good about the number, and hand back the savings through reconciliations you did not model. The rent looked like a deal. The base year made it one for the landlord.

Where to push: ask what the building’s occupancy was in your proposed base year, and ask for the prior two to three years of actual operating-expense statements. If costs are trending up sharply or occupancy was low, that is your signal to insist on a later, fuller base year — or to solve it with a gross-up provision, below.

Expense stops set below run-rate

An expense stop is the base year’s cousin, common in medical office and often written into new or renovated buildings. Instead of tying your floor to an actual reference year, the lease names a fixed dollar-per-square-foot figure — the “stop” — that the landlord covers. You pay everything above it.

The mechanics are cleaner, but the trap is identical: if the stop is set below what the building actually costs to run, you are paying overage from day one. A stop is only protective when it is set at or above the building’s real, stabilized operating cost. Set below run-rate, it is base rent by another name — money you pay on top, dressed as a cost you only owe “if expenses rise.”

Where to push: treat the stop like the base year. Ask for the building’s actual per-square-foot operating cost and make sure the stop is set at or above it, not at a number that guarantees you an overage bill in month one. If the landlord will not share actuals, that reluctance is itself information.

Gross-up: the provision that actually protects you

Most operating-expense language favors the landlord. The gross-up provision is the rare clause that, written correctly, protects the tenant — and you frequently have to ask for it by name.

A gross-up says that when the building is less than fully occupied in any year, variable operating expenses are calculated as if it were fully occupied — typically normalized to full or near-full occupancy. That sounds like it helps the landlord, and in one narrow sense it does. But its real effect is to neutralize the low-base-year trap: it raises the base-year figure to what a full building actually costs, so that later, when the building fills up, there is no artificial “increase” to bill you for. It makes the base year honest.

The rule of thumb: you want gross-up applied to both the base year and every comparison year, on a consistent basis. Grossing up only the later years while leaving a deflated base year is worse than no gross-up at all — it manufactures the exact gap you are trying to close.

Where to push: ask for a gross-up provision if the lease lacks one, and read the one you have carefully. Confirm it applies to the base year, that it normalizes to the same occupancy level in every year, and that it covers only variable (occupancy-driven) costs, not fixed ones. The standard normalization level is around 95% occupancy (some landlords push for 100%); a lower figure quietly shrinks the protection.

Property-tax reassessment risk

Property taxes deserve their own line of attention because in Washington they move on a schedule you do not control. The county assessor revalues property on a regular cycle, and a change in ownership or a new assessment can push the tax line materially higher than it was in your base year — with the entire increase flowing to you as an overage.

The scenario that stings: you sign in a building that recently sold or was just built. Your base year captures the old, lower assessment. The reassessment catches up a year or two later, taxes jump, and because it registers as an “increase over base,” it is yours to pay in full through reconciliation. In Washington the assessor revalues property every year, so that catch-up can land as soon as the next cycle — address in writing how a post-sale reassessment flows through your base year.

Where to push: address reassessment in writing. Two protections are worth asking for — a carve-out that excludes tax increases driven by a sale or transfer of the building during your base year from being passed through, and a cap on the annual increase in the tax component (or in controllable operating expenses generally). At minimum, do not let a known, imminent reassessment sit inside a base year you are treating as normal.

What this comes down to

The base year, the expense stop, and the gross-up are three settings on the same dial: how much of the building’s rising costs land on you, and how fast. None of them changes the rent on page one. All of them change what you actually pay by year three — and none of them is negotiable after you sign.

The moves are simple and they are all made in the window before signature: set the base year to your first full year of occupancy, get the actual expense history, insist on a gross-up that covers the base year, and put reassessment protection in writing. A landlord’s broker will rarely volunteer these. A tenant-side broker will — and because the landlord customarily pays the tenant broker’s commission, having that read in your corner typically costs the practice nothing.********