我觉得他如果不加入Medicare还是可以拿ACA补助，因为Medicare Part A要交费

Publication 974有说：

“Exceptions.

While you are generally considered eligible for government-sponsored MEC (and are ineligible for the PTC) if you are able to enroll in that coverage, you are considered eligible for government-sponsored coverage under the following programs only if you are enrolled in the program.

4. Coverage under Medicare Part A for which the individual must pay a premium.”

就是说，既然你Medicare Part A要交premium，如果你不是enrolled in Medicare Part A，你不算eligible for government-sponsored coverage，所以还是可以拿PTC。