Which document must be provided to investors before their purchase of a mutual fund?

Investors must be provided with a prospectus before their purchase of a mutual fund because it contains essential information about the investment, including details on the fund's investment objectives, fees, performance history, and risks involved. The prospectus serves to inform potential investors, allowing them to make an educated decision about whether or not to invest in the fund.

While an annual report provides updates on the fund's performance and financial statements, it is typically issued after an investor has already purchased shares. An offering memorandum is usually associated with private placements and is not standard for mutual fund investments. A fiscal statement is not a recognized document relevant to mutual fund transactions in this context.

By ensuring that investors receive a prospectus before any purchase, regulators aim to promote transparency and protect investors by providing them the necessary information to understand the investment they are considering.