Steve,
Here in The Netherlands (and in Germany at least), a Purchase Order is a signed agreement where one party agrees to purchase the goods and/or services of another. It is – in effect – a Subcontract, but it fails dismally to provide for all the bells and whistles that a Subcontract should, including the relevant rights and obligations of the Parties under the Main Contract.

To my mind a PO should only be used for ordering staples for the stapler and paper for the printer, and NOT for setting out even the simplest of contractual rights and obligations. Luckily, I am now having some success here in The Netherlands in getting my Dutch Clients to move away from a PO set up and to use Subcontracts instead (The Germans are more resistant to change!!)

By the same token, a Work Order here is the same as a site-generated Variation (or Change) Order, where a Contractor or Subcontractor is issued with an instruction to work in a varied manner.

In all, it really depends on the local usage of these terms. If they are not specifically defined in the Contract Terms (and they should be…!), then ask around locally and see what the perceived definition is! I am sure the definitions of these terms will all be different the world over!!

Hope this helps.

Stuart

www.rosmartin.com