Socratic lens
Test the assumption.
Ask what is being taken for granted, whose evidence matters, what a counterexample would show and who lives with the consequence.
What decision is actually being made, by whom, for what purpose and over what time horizon?
Which assumption is doing the most work in my structure, and what evidence would overturn it?
Could the arithmetic be correct while the model of the business is wrong—and how would I notice?
Does my recommendation follow from the evidence, including facts that complicate the answer?