Remain and Leave campaigners in the EU referendum reported almost £6.5m in donations in the four weeks to 9 June, says the Electoral Commission.
Leave declared almost £3.6m in donations compared with Remain's £2.9m, during the period from 13 May.
In total, registered EU referendum campaigners have reported more than £27m in donations and £6m in loans and credit facilities since 1 February.
Voters go to the polls on Thursday to decide on the UK's future in the EU.
The figures published by the watchdog, external - in the latest of their pre-poll donation reports - details money reported by campaigners spending more than £10,000 in the referendum and individual donations of more than £7,500.
They show that registered campaigners for both Remain and Leave declared a combined total of £6,484,911 over the 25-day period.
Public grant
The various campaigns for Britain to leave the EU declared a combined £3,596,994 in donations, of which £2,708,994 was to the officially designated Out campaign, Vote Leave.
Grassroots Out - which lost out to Vote Leave in the race for the official campaign designation - declared £125,000.
A total of £2,887,917 was donated to the Remain campaigns, with the official Britain Stronger in Europe receiving £1,886,055 of that.
Five of the top eight biggest individual donations went to Vote Leave, including £1m from Diana Van Nievelt Price.
Britain Stronger in Europe also received a £1m donation - from travel company Trailfinders Limited.
There was just one loan, of £10,000, from Referendum Facts Ltd, to Remain.
Vote Leave and Britain Stronger In Europe have now each received the £600,000 public grant that they are entitled to as the designated campaigns.
