After Third Avenue HY fiasco/collapse/freeze, the SEC came up with fund liquidity rules [15% limit on illiquid holdings; enough liquidity to allow redemptions within a few days, etc] that require a discussion of fund liquidity status in fund reports. Now we have another disaster in IOFIX - just a huge loss but the fund remains OEF so far.
Unfortunately, the related documentation on fund liquidity at SEC is quite dense and many other media links are quite superficial. These apply to OEFs and ETFs; this isn't an issue with CEFs or interval-funds. The following are some readable links.
https://www.ici.org/faqs/faq/mfs/faqs_mf_liquidity "Under the Investment Company Act of 1940, a fund has up to seven days to pay proceeds to shareholders who redeem shares; in practice, funds usually pay redemption proceeds even sooner, within one or two days of the redemption request. Because of this requirement, the Securities and Exchange Commission (SEC) has issued guidance that limits a fund’s “illiquid assets” to 15 percent of the fund’s net assets. In October 2016, the SEC adopted a liquidity risk management program rule and related reporting and disclosure requirements applicable to mutual funds and open-end ETFs, which will supersede this current guidance and substantially enhance funds’ regulatory obligations in this area. For most funds, the compliance dates for most of these new requirements is December 1, 2018 or June 1, 2019, depending on the requirement." [blue highlights mine]