Currency & exchange rates — Set the workspace's currency

In Settings, each workspace you administer has a Currency setting. Leave it on Follow the owner and it uses the preference of whoever owns the workspace, which is almost always right and means a new workspace needs no setup at all. Choose a currency explicitly to pin it. Changing it never rewrites a stored amount and converts nothing. It changes what the numbers already on your records are understood to be in, so change it because it was wrong, not to convert your data.