The IRS defines a (home) improvement as something that “materially adds value to your home, considerably prolongs its useful life, or adapts it to new uses.

This eliminates minor upgrades like a $30 light fixture.

An example the IRS makes to clarify the distinction between an improvement and not an improvement is a roof. If you replace the entire roof, it is an improvement. If you only replace part of the roof, it is not an improvement.

Yeah, it adds $30 to the cost basis. But you’ll go crazy keeping track of every nickel and dime that you spend on house improvements.

Cosmetic changes do not increase the cost basis.
Repairs do not increase the cost basis.

If the bathroom had no exhaust fan, and you added an exhaust fan, I would argue that you increased the cost basis by $30 because you added value to the home. If you merely replaced a fan, then that would be a repair and would not qualify.

No, a new fan does not add to the cost basis. That’s a cosmetic improvement and not integral to the structure or value. Putting an addition on your home, Replacing an entire roof, Paving your driveway, Installing central air conditioning or Rewiring your home all WILL add to the cost basis.

Typically only significant repairs, that increase the life of the home, or the value of the home would be capitalized into the cost. Still, even these types of expenses are open to intrepretation.

A $30 fan for the washroom does not fit into the above description, so NO.

You need to talk to an appraiser. This is usually well worth the investment. They will tell you specifics for your home, the little things you can do for the most return. Alot of people do a remodel to ready their home for sale without ever checking to see if the improvements will actually help the market value. Big mistake.