In Maryland, the tax people re-assess your property every three years. I can remember my taxes going down twice.
The first time, was back in the 1990s. I had bought a condo in late 1994, and initially, the property tax bill was around $900/yr. I think it dropped to around $700 at some point a few years later, but by the time I sold in 2004, was back up to around $900.
Actually, now that I think about it, I don't think the actual tax bill came down in the wake of the Great Recession, although the assessment certainly did. I do remember at my peak, the overall bill was around $5,000, but there was an ~$1800 homestead tax credit that brought it down to around $3200. The next year, when the lower assessment kicked in, I think the whole bill was around $3200. They took the reduction in assessed value out against the homestead tax credit first, before applying it to the remaining part of the bill.
When it comes to improvements to the property, assessments can be funny. At the old place, I had a 24x40 garage built in 2006, and it never altered the assessed value, or the property tax bill. At least, not by any meaningful amount.
I bought my current place in 2018. I lucked out with the taxes, because for their purposes, it was only listed at 960 square feet. Ironically, the same size as the garage I had built, 24x40. In 2008, the lady I bought the house from put an addition on the front to make it L-shaped, and added a second story. It's now around 2440 square feet, plus 432 for the sunroom, and 960 for the basement. The real estate listing called it 2872, including the sunroom as "living space".
Well, the assessment finally caught up to that 2008 construction in 2019, when "above grade living area" was finally increased. But, somehow they came up with the number of 3929 square feet!
I had a garage built at the new place, 36x60, with a loft that's around 15x60. It got its final inspection/approval from the county in April of 2022, so I'm sure it's not showing up on any kind of assessment yet.
I was sort of tempted to try and fight that 3929 square foot estimate, since they're basically charging me for about 1050 square feet that I don't have. And even more, depending on what you consider the sunroom to be. I think of it as an enclosed porch, and not really an integral part of the house. But, where I live, no secondary structures are allowed to be larger than the primary, so at the actual square footage, they would not have allowed me to build the garage I wanted. At the very least, I would have had to have lost the loft.
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