Ask what is missing. We will have written it down.

Scope comes first, because scope decides the size of everything after it. Everything removed is logged, so the removals can be inspected. You get the rules as well as the rows, so the build can be repeated.

Legal-entity grouping

Deciding whether branches roll up to one parent or stand alone, and applying it consistently.

Currency handling

Stating the unit and basis for any monetary field instead of leaving it implied.

Hand-off

Delivered in the format your systems take, with the field definitions written down.

A short brief is enough to start; detail can follow once the size is known.