At which stage in a negotiation would questions be asked to obtain missing information?

There are 5 key phases of negotiation:

The opening phase: confirm understanding and get the issue on the table

The testing phase: check assumption and confirm understanding

The proposing phase: asking 'if'

The bargaining phase: using tradeables

The agreement and closing phase

The testing could take the form of questions following a presentation by either side or questions on a tender or proposal document received by the buyer from the potential supplier. The testing phase is necessary to confirm that your approach and objectives are appropriate for the negotiation situation you now find yourself in. Careful listening, observation and interpretation of TOP's responses may give indication of the following:

Areas where TOP is willing and unwilling to make concessions

What factors or issues TOP places a high value on

If there are any non-commercial or emotional factors that may be pertinent

TOP's underlying interests - why they are taking the position they are.