谢谢，我今天在nolo上看到一个例子，他把维修和improvement合起来算了，产生了我的疑问。

Example of SHST In Action

Sam owns a single family home that he rents out. It has a $100,000 unadjusted basis (that is, it cost $100,000). During 2014, he paid $200 to a plumber to fix a leak, repaired a window for $400, and replaced the home's water heater for $1,200. Sam qualifies for the small taxpayer safe harbor because the $1,800 he spent on repairs, improvements, and maintenance during 2014 is less than 2% of his building's unadjusted basis (2% x $100,0000 = $2,000). By filing an election to use the SHST, Sam may currently deduct the entire $1,800 on his 2014 IRS Schedule E. This is so whether or not any of these expenses, such as the water heater replacement, might constitute an improvement under the more complicated IRS repair rules that apply in the absence of a safe harbor.