A probe is understood to have been launched at the HQ of the Knights of St Columba five months ago.
The Catholic men-only order is the largest of its kind in the UK with 4000 members.
The order is noted for raising funds for projects such as assisting health in the developing world and earthquake relief, and projects in Britain.
The head of the KSC is Ron Lynch, who holds the position of Supreme Knight. Its board is due to meet in Preston next month.
A police spokeswoman said: "We are investigating a report of the misappropriation of money from the Knights of St Columba.
"Enquiries are continuing."
Founded in 1919, the KSC are named in honour of Saint Columba, a Christian missionary from Ireland.
Membership is limited to practising Catholic men over the age of 16.