Hi,
IVS and Red Book don't require valuers to use one or more approaches. The choice is only and always on the valuer's professional judgement and responsibility.
I'm pasting hereafter the relevant paragraphs from IVS 2022 (as you know, IVS are currently updating and the new edition will be effective from January 2025, but there will be no relevant changes on these topics).
I hope it's of some use.
Best. Maurizio
IVS 104 Bases of Value
30.6. The data available and the circumstances relating to the market for the asset being valued must determine which valuation method or methods are most relevant and appropriate. If based on appropriately analysed market-derived data, each approach or method used should provide an indication of market value.
IVS 105 Valuation Approaches and Methods
10.1. Consideration must be given to the relevant and appropriate valuation approaches. One or more valuation approaches may be used in order to arrive at the value in accordance with the basis of value.
10.3. The goal in selecting valuation approaches and methods for an asset is to find the most appropriate method under the particular circumstances. No one method is suitable in every possible situation.
10.4. Valuers are not required to use more than one method for the valuation of an asset, particularly when the valuer has a high degree of confidence in the accuracy and reliability of a single method, given the facts and circumstances of the valuation engagement. However, valuers should consider the use of multiple approaches and methods and more than one valuation approach or method should be considered and may be used to arrive at an indication of value, particularly when there are insufficient factual or observable inputs for a single method to produce a reliable conclusion.
40.2. The income approach should be applied and afforded significant weight under the following circumstances:
(a) the income-producing ability of the asset is the critical element affecting value from a participant perspective, and/or
(b) reasonable projections of the amount and timing of future income are available for the subject asset, but there are few, if any, relevant market comparables.
40.3. Although the above circumstances would indicate that the income approach should be applied and afforded significant weight, the following are additional circumstances where the income approach may be applied and afforded significant weight. When using the income approach under the following circumstances, a valuer should consider whether any other approaches can be applied and weighted to corroborate the value indication from the income approach:
(a) the income-producing ability of the subject asset is only one of several factors affecting value from a participant perspective,
(b) there is significant uncertainty regarding the amount and timing of future income-related to the subject asset,
(c) there is a lack of access to information related to the subject asset (for example, a minority owner may have access to historical financial statements but not forecasts/budgets), and/or
(d) the subject asset has not yet begun generating income, but is projected to do so.