What is an SPA (sales and purchase agreement)?

The sales and purchase agreement is the contract. Letters of intent, purchase orders and corporate offers all describe an intended trade; the SPA creates the obligations. It is signed by both parties and it supersedes everything that came before it.

That last point is worth stating plainly, because it is where deals are lost. A tolerance agreed by email, a rejection threshold discussed on a call, an inspection agency someone assumed — none of it survives unless it appears in the SPA. Entire-agreement clauses exist precisely to make prior understandings unenforceable.

Quality: the specification with typical and rejectable values for every element that matters, the sampling and assay method, and the price adjustment for grade above or below the base. Quantity: the nominal figure and the tolerance, and whose option it is to load within it.

Delivery and risk: the Incoterm and version, the load and discharge ports, the laycan, and the demurrage and despatch rates. Payment: the instrument, the trigger, the document set, and whether payment is provisional against a final assay. Governing law, arbitral seat and rules — and, for anything crossing a sanctioned or high-risk jurisdiction, an explicit sanctions clause.

Not usually over price. The recurring disputes are about quality at discharge against quality at load, which is why the umpire procedure and the tolerance for laboratory variation matter more than they look; and about time, where a vague laycan and an unspecified demurrage rate produce a claim nobody can quantify.

The other frequent failure is the payment trigger. "Payment against documents" means little unless the document set is listed and the presentation period stated. A short, specific, complete SPA is worth more than a long one that leaves those definitions to be argued about later.