Every money market fund advertises a gross yield. The number you actually earn is lower, because a 15% withholding tax is deducted at source before the interest reaches you.

Take KES 100,000 placed at a 12% gross annual yield. Gross interest is KES 12,000 over a year. The 15% tax removes KES 1,800, leaving KES 10,200 in your pocket. Your real, after-tax yield is 10.2%, not 12%.

This is why comparing funds on gross rate alone is misleading. A fund quoting 12.4% gross and one quoting 12.0% gross are only 34 basis points apart after tax, not 40. Always compare on net.