Final answer:
Having a current rating of investment grade is not a major requirement for shelf registration, which allows companies more flexibility in offering securities over time.
Step-by-step explanation:
The major requirements needed to qualify for shelf registration include having outstanding stock with a market value in excess of $150 million, not defaulting on debt in the past three years, and having no violations of the Securities Act of 1933 or the Securities Exchange Act of 1934 in the past three years. The requirement that is not a major one for shelf registration is having a current rating of investment grade. Shelf registration allows companies to register securities with the SEC, but they don't need to sell them immediately and can instead offer them over a period of time (up to three years), which offers flexibility and efficiency in raising capital.