Market
Market is the country your organisation trades from. It sets the tax and identifier labels and the defaults for private bids, such as the buyer's country. It never changes which procurement rules apply to a public bid. With no market saved, one is suggested from your address country, and nothing is stored until you save.
Default currency
Default currency is the currency a new value starts in, for example a private bid, a private requirement, a quick quote or a Quick RFQ. It is a preselection you can change on each value. CrowMark never converts a stored value, and this is not the currency you are billed in.
Where to set them
Both are asked when you set up your organisation, and can be changed at any time in Settings, Organisation, General by an owner or an admin. A Companies House lookup on the same page fills the name, number and address for a UK company.