請你把出處貼出來看。
At best you need to apply for a permit to mitigate the unpermited work, that an inspector will come and open up walls to inspect all plumbing, electrical etc. and fix all the work that is not up to code.
Depend on how long ago the work was done, even if it met the code at that time, it might not meet the code now. So you might have to redo a lot of things.
That is the BEST outcome. In other places they won't do remedial permit.