Retained Interest is held on account by CrowdProperty, this is then dispersed via methods, this is clearly labelled on the project information provided at pledging:
Method 1 – Interest will not be paid out monthly for retained interest until a partial repayment has been made by the borrower of the loan.
Method 2 – Retained Interest is taken and paid out monthly for every loan part, for legacy loans where this previous main method has already been started. This is to maintain parity with all loan parts, some of which will fund after March 2025.
Method 3 – Retained Interest taken only for the first loan part. For these legacy loans if retained interest is being paid out monthly, this will continue.