On a launched product, cost of sales. On an unlaunched product, cost of inventory, etc. One of the key questions that defines "R&D" is technical risk: are you

On a launched product, cost of sales. On an unlaunched product, cost of inventory, etc. One of the key questions that defines "R&D" is technical risk: are you answering a question of "Can it be done?" or "How can we do it?" If you know how and you are just slapping it together, it's an opex.