Budget
Whether funds exist or can realistically be obtained for a purchase of this size. The useful version of this question is not whether a line item has been approved, but whether the organisation spends money on problems of this kind and who signs those cheques.
Authority
Who can approve the decision, and how much influence your contact has over them. Asking directly whether someone is the decision maker rarely produces an accurate answer, because most people describe themselves as more influential than the process treats them.
Need
Whether there is a business problem serious enough that the organisation would spend money and disruption to solve it. Interest is not need. Need has a cost attached to doing nothing.
Timeline
When a decision is expected, and crucially why then. A date that is anchored to something happening in the business, a contract expiry, an audit, a launch, a season, is planable. A date offered to close a conversation politely is not.
A worked scoring example (illustrative)
Score each criterion zero to two, where zero is unknown, one is indicated by the buyer, and two is confirmed with something specific. An enquiry might score: budget 0, authority 1, need 2, timeline 1, for a total of four out of eight. The number alone is not the point. This lead has a clearly articulated problem, is talking to someone with partial influence, has mentioned a rough period, and has said nothing about money. The correct next action is not to disqualify it but to establish who approves spending of this type and what the problem is currently costing. A second enquiry scoring budget 2, authority 2, need 0, timeline 2 is the more dangerous of the two, because everything is in place except a reason to act.