Question:

Is it acceptable for an appraisal fee to be based on a percentage of the value conclusion?

Response:

No, the Management section of the ETHICS RULE states: 

It is unethical for an appraiser to accept an assignment, or to have a compensation arrangement for an assignment, that is contingent upon any of the following:

1. the reporting of a predetermined result (e.g., opinion of value);

2. a direction in assignment results that favors the cause of the client;

3. the amount of a value opinion;

4. the attainment of a stipulated result; or

5. the occurrence of a subsequent event directly related to the appraiser’s opinions and specific to the assignment’s purpose. (Bold added for emphasis)

This is reiterated in the signed certification (Standards Rule 2-3, 3-3, 5-3, 6-9, 8-3, and 10-3,) that must be included in each appraisal, appraisal review, or appraisal consulting report.