Safe harbor reporting requirements for Form 4684. If you use one of the safe harbor methods provided in Revenue Procedure 2018-08, you must attach a statement to Form 4684 stating that you used Revenue Procedure 2018-08 to determine the amount of your casualty loss. Include the specific safe harbor method used. If you use the cost indexes safe harbor method provided in Revenue Procedure 2018-09 to calculate hurricane-related losses, you must attach a statement to Form 4684 stating that you used Revenue Procedure 2018-09 to determine the amount of your casualty loss. Include the specific table number used. When completing Form 4684, do not enter an amount on line 5 or line 6 for each property. Instead, enter the decrease in the FMV determined in the relevant safe harbor method on line 7.
in other words, you will no longer be able to e-file if using either procedure. at the top of 4684 write the rev proc number using are using - ie filed pursuant to rev proc 2018-X.
you should read the instructions for form 4684
sectipn A of the form for personal property section B for business property.
