I own a cottage in Ontario and have had to file the UHT for 2 years now. My wife is also listed on the property deed, and she needs to file a separate (and duplicate) return. Fortunately, for seasonal cottage owners there are currently some exemptions that eliminate the 1% fee. If not for those exemptions, we would need to stay 28 nights a year, either me or her, or both of us combined (counts as 1 night). Loaning the cottage out to any of my friends or family does not count - it has to be property owner.
The first year we had to file the return, I was stumped on how I would remember the number of nights we were there - then I looked at my Google Maps and realized it tracked my every move, even our stops along the way for gas, groceries, etc. All on my Google Maps. So even if I lied and said I did stay there 28 nights, they could verify when and where I was at all times. Even my vehicle has a GPS tracker with this information, not just my phone.