(21)If both the resolution entity or the parent and its subsidiaries are established in the same Member State and are part of the same resolution group, the resolution authority should be able to waive the application of the MREL that applies to those subsidiaries that are not resolution entities or to permit them to meet the MREL with collateralised guarantees between the parent and its subsidiaries, that can be triggered when the timing conditions equivalent to those allowing the write down or conversion of eligible liabilities are met. The collateral backing the guarantee should be highly liquid and have minimal market and credit risk.