An Oil Tank Guess That Cost More Than It Should Have

The situation

On the morning of closing, the sellers' agent called the buyers' lawyer with a problem. The fuel company that would normally send a truck to dip the oil tank and confirm exactly how much fuel remained could not get to the property that day. Rather than delay closing, the agent proposed using an estimate: the seller, Alejandro, would state how much oil he believed was in the tank, and the statement of adjustments would credit him for that amount instead of a measured reading. It was framed as a formality, a one-line fix to keep a busy closing day on schedule.

Sylvain, a semi-retired specialist physician, and Danielle, a retired business owner, were buying a property outside Collingwood for roughly $1,650,000 as the next stage of a long-planned downsizing. They had sold a much larger home, arranged their financing carefully, and wanted nothing more than a clean, uneventful closing after a stressful few months of packing, moving, and coordinating two closings on the same week. The oil tank adjustment was a small line item in a large transaction, and their instinct, like most buyers on closing day, was to accept the seller's estimate and move on so the day could proceed on schedule.

Their real estate lawyer flagged the request before it went further. A statement of adjustments exists to settle exactly this kind of shared cost fairly between a seller who has prepaid for something the buyer will consume, or a buyer who will pay for something the seller already used. Oil is one of the few adjustment items with a genuinely measurable answer: a dip test tells you, within a narrow margin, how many litres are in a tank. An estimate supplied by the party being paid for that estimate is a different thing entirely, and on a $1,650,000 purchase with a full oil tank, the gap between a generous estimate and an accurate one can run into several thousand dollars, particularly on a large rural property where the tank itself is sized to last most of a winter.

Because closing was scheduled for early that afternoon and neither side wanted to reschedule, the parties agreed to close using Alejandro's estimated figure, with a signed undertaking that the actual fuel level would be measured within two weeks and the adjustment corrected if it was wrong. That undertaking, entered into almost as an afterthought to save the closing date, became the only lever available once the real number came back. At the time, it barely registered as a decision at all. In hindsight, it was the single choice in the whole transaction that mattered most.

Danielle later said the tank never crossed her mind as a risk. She and Sylvain had spent weeks worrying about mortgage discharge timing, moving trucks, and whether their furniture would fit the new layout. A line item measured in litres of heating oil felt, on the morning of closing, like the least of their concerns.

What the law actually said

A statement of adjustments is not a formality; it is a binding accounting between the parties, prepared under the agreement of purchase and sale and the closing documents that flow from it. Items like property tax, utilities already paid, and fuel in a tank are adjusted so that each party pays only for what belongs to their period of ownership. When both sides sign off on a statement of adjustments and the deal closes, the figures on it are generally treated as final, which is exactly why Sylvain and Danielle's lawyer insisted on the written undertaking before agreeing to use an estimate at all.

An undertaking given on closing is a serious promise between lawyers, not a casual assurance between the parties themselves. When a lawyer undertakes that a figure will be verified and corrected, that promise is enforceable through the law society's own rules, independent of whatever happens between the buyer and seller personally, and a lawyer who fails to honour an undertaking risks professional consequences that have nothing to do with whether the underlying dispute is large or small. This is what gave Sylvain and Danielle's file its turning point: because Alejandro's own agent had proposed the estimate and Alejandro's own lawyer had signed the undertaking to correct it, the burden of proving the true fuel level, and of honouring whatever that proof showed, sat with the seller's side, not the buyers'. Had the buyers' lawyer simply accepted the estimate as final on closing day, none of what followed would have been possible.

The complication was that an oil tank is a depleting asset. Every day between closing and the eventual measurement, the new owners were using fuel to heat the property, which meant the tank was legitimately emptying regardless of who was right about the closing-day figure. A dip test performed two weeks after closing does not simply reveal what the tank held on closing day; it has to be reconciled against how much fuel the household consumed in the meantime, using delivery and consumption estimates that are themselves imprecise. No court or law society rule can make an already-burned litre of oil reappear for measurement.

That reconciliation problem is what limited how much could ultimately be recovered. The law supported Sylvain and Danielle's right to an accurate adjustment and gave them a signed undertaking to enforce it. It could not undo the fact that, by the time anyone could prove the original estimate was wrong, some of the disputed fuel had already been burned proving it. The undertaking guaranteed a correction; it could not guarantee that the correction would be complete.

It also mattered that the undertaking specified a two-week window rather than leaving the timing open-ended. An undertaking without a deadline invites delay, and delay in a fuel dispute works entirely against the buyer, since every additional day narrows the gap between the disputed estimate and whatever the tank eventually measures. Because the deadline was fixed in writing at closing, Alejandro's lawyer could not simply let the matter drift.

What we did

1. Insisted on a written undertaking before closing, not a verbal assurance. When the estimate was first proposed, we required Alejandro's lawyer to sign a formal undertaking to measure the tank and adjust the price within a fixed window, rather than accepting the agents' informal promise, because only a lawyer's undertaking carries a real professional consequence if it is broken and only a fixed window prevents the correction from simply drifting.
2. Requested the fuel company's delivery history for the property. Before the two-week measurement window closed, we asked for records of the last several oil deliveries covering roughly the prior two heating seasons, which gave an independent baseline for how much fuel a full or near-full tank should have held, rather than relying solely on Alejandro's verbal estimate of the level.
3. Arranged an independent dip test through our clients' own fuel supplier. Rather than accepting a reading arranged by the seller's side, or leaving Alejandro's agent to choose who performed it, we had Sylvain and Danielle's new supplier perform the measurement on a fixed date within the undertaking window, using a company with no stake in the outcome, so the result could not later be characterised by either side as one-sided, delayed for convenience, or timed to favour whoever had arranged it.
4. Built a consumption estimate for the intervening period. Using average heating-degree consumption for the property's size, the season, and the number of days since closing, we calculated a reasonable range for how much fuel had been used in the two weeks before the test, so the final adjustment reflected the tank's condition on closing day rather than on the day of the test itself.
5. Presented the gap in writing and demanded correction under the undertaking. The measured figure, once adjusted for the intervening consumption, showed the tank had held meaningfully less fuel at closing than Alejandro's estimate claimed. We set out the shortfall, the supporting delivery records, and the consumption calculation in a formal letter, and called on the undertaking to be honoured within a set number of days.
6. Negotiated the disputed margin rather than litigating it. Alejandro's lawyer accepted the bulk of the shortfall but pushed back on the consumption estimate for the two-week gap, arguing some portion of it was unavoidable measurement imprecision rather than overstatement. Rather than incur legal costs disputing a relatively small residual amount, we negotiated a final figure that captured the clear overstatement while conceding the genuinely uncertain portion.
7. Confirmed the correction and closed out the undertaking in writing. Once payment was received, we confirmed in writing to Alejandro's lawyer that the undertaking had been fully satisfied and that no further claim would follow, which protected both sides from any later suggestion that the matter remained open. Closing the undertaking formally mattered for Alejandro's lawyer too, since an unclosed undertaking sits as an open professional obligation until the other side confirms it has been met.
8. Advised our clients on what to expect for future closings. We explained, in plain terms, why they should ask for a measured reading rather than an estimate whenever it is offered on closing day, even when it feels like the path of least resistance under time pressure, and why a signed undertaking with a deadline is worth the extra sentence of paperwork it takes to obtain.

The outcome

Sylvain and Danielle recovered most, though not all, of the difference between Alejandro's closing-day estimate and the tank's actual measured contents. The corrected adjustment, paid roughly six weeks after closing, put several thousand dollars back in their pocket, but the negotiated compromise over the consumption gap meant they absorbed a smaller, unrecoverable portion of the loss themselves. In plain terms, they got most of their money back, not all of it, and they got it months later than they should have needed to ask for it at all.

The written undertaking is what made any recovery possible at all. Without a lawyer's formal promise to correct the figure, the couple would have had only a verbal assurance from the seller's agent, difficult to enforce and easy to dispute once the deal had closed and Alejandro had no further reason to cooperate. Because the undertaking existed, the seller's own lawyer was professionally obligated to see the correction through, and that obligation did not depend on Alejandro personally agreeing that he had overstated the reading.

What the file could not fix was the time value of getting it wrong in the first place. Sylvain and Danielle spent the weeks after what should have been a simple closing gathering delivery records, arranging an independent test, and negotiating a figure that, by rights, should have been correct from the start. None of that work was compensated on its own; it simply had to be done to recover money that was theirs from the outset.

The lesson they took from it, and the one we now give every client facing a similar shortcut on closing day, is that an estimate offered under time pressure is worth asking to postpone for a day rather than accepting and hoping it holds up. A delayed closing is an inconvenience. An unmeasured adjustment on a seven-figure property is a real financial exposure dressed up as a scheduling favour, and the two are not the same size of problem.

What you can learn from this