The Commissioners of Irish Lights (CIL) is a "not for profit" organisation and, along with Trinity House and the Northern Lighthouse Board, derives its income mainly from the charging of light dues on commercial shipping entering British and Irish ports. Additionally fishing vessels in Northern Ireland are charged an annual light due payment consistent with UK fishing vessel owners. CIL, TH, and NLB operate an integrated system of aids to navigation around Britain and Ireland

The current rates for Light Dues on commercial vessels as of 1st August 2009 are:

UK and Northern Ireland 39 pence per tonne (sterling)
Republic of Ireland 57 cent per tonne (euro)

The rate is applied to the net registered tonnage (NRT) of the vessel. A tonnage cap of 35,000 tonnes applies.

The Minister for Transport reviews the rate for Ireland annually under an Order of Section 2 of the Merchant Shipping (Light Dues) Act, 1983.

Regular traffic into ports in Ireland and the UK are only obliged to pay for a maximum of 9 voyages a year. This is a unified policy, which operates throughout the British Isles.

All Light Dues collected in the UK and Ireland are "pooled" in a central fund called the General Lighthouse Fund (GLF). The Secretary of State in the Department for Transport in London administers this fund. Operating funds are released to Trinity House, Northern Lighthouse Board and Commissioners of Irish Lights from the GLF. Under an agreement reached between the Irish and UK Authorities in 1985, Light Dues collected at Irish Ports are supplemented by an annual Irish Government Exchequer contribution to the General Lighthouse Fund.