I agree, you use the form that matches the beginning of the plan year, but in this case, I'm not sure the plan year is correct. Does the plan year begin on July 31 or does it end of July 31? Is the question about the 8/1/2017 to 7/31/2018 (2017 5500) or is it 8/1/2018 to 7/31/2019 (2018 5500)?