A tax-exempt return means that no withholding tax is deducted from your investment income. In Egypt, certificates of deposit (CDs) and savings accounts at licensed banks are tax-exempt: the stated annual rate is your net rate. There is no further tax deduction at source.
This is a significant advantage: two products with the same headline rate — one tax-exempt and one subject to 20% WHT — have very different real returns. Tax exemption makes the product's gross rate equal to its net rate, simplifying comparison and maximizing the investor's actual take-home return.