Business Definition for: tranches Dictionary of Finance and Investment Terms tranches risk maturity or other classes into which a multi-class security, such as a Collateralized Mortgage Obligation (CMO) or a REMIC is split. For example, the typical CMO has A, B, C, and Z tranches, representing fast pay, medium pay, and slow pay bonds plus an issue (tranch) that bears no coupon but receives the cash flow from the collateral remaining after the other tranches are satisfied. More sophisticated CMO versions have multiple Z tranches and a Y tranch incorporating a sinking fund schedule. in the United Kingdom, fixed-rate security issues are often prearranged by governments, local authorities, or corporations, then brought out in successive rounds, termed tranches. One thus speaks of new tranches of existing securities. A variation of the term, tranchettes, refers to small tranches of gilt-edged securities (government bonds) sold by the government to the Bank of England, which then sells them into the market at times it deems appropriate. subunits of a large ($10-$30 million) Eurodollar certificate of deposit that are marketed to smaller investors in $10,000 denominations. Tranches are represented by separate certificates and have the same interest rate, issue date, interest payment date, and maturity of the original instrument, which is called a tranch CD.