A simple question lies behind Patrick de Kruyff’s Tax Court of Canada victory last month over the Canada Revenue Agency (CRA): Who on earth would suggest taking Toronto’s Don Valley Parkway at rush hour?

An auditor in Vancouver, that’s who.

The basic rule for the deduction is that the move has to cut at least 40 kilometres off the daily commute.

But for some reason Google Maps kept giving the CRA a much shorter route than it did de Kryuff, despite the fact they both punched in the same coordinates at the same time of day Monday to Friday — the heart of rush hour, 4:45 p.m.

And then de Kruyff found the flaw that led to a precedent-setting ruling that could pave the way for tax relief for other urban commuters: the CRA’s employee was in B.C. — getting Google Maps’s suggestions to navigate Toronto traffic at 4:45 p.m. Pacific time.

That’s 7:45 p.m. Eastern.