Another £4.7m will be spent on regulation and campaign mailshots.
Legitimate, perhaps, has been the squealing from Hillary Clinton about a mailshot sent out by the Obama campaign in Ohio branding her a long-time supporter of the North American Free Trade Agreement (Nafta).
They are also entitled to campaign broadcasts and free mailshots.
Hammond said to Bone: "If [your] concern is that the government are thinking of spending public money to deliver doorstep mailshots in the last four weeks of the campaign, I can assure him that the government have no such intention.
The consultation on the review ends on Friday – and campaigners are urging a mass mailshot to impress on ministers the need for action.
The costs of allowing each of the main campaign organisations - Yes Scotland and Better Together - a free mailshot to every elector or household in Scotland.
Mr Sykes, aged 55, has set up an office in Harrogate, North Yorkshire, to mobilise his campaign, although he will subcontract work such as mailshots as it gains momentum.
The two official campaigns can spend up to £7m each on campaigning, with £600,000 in public funds, and get a free mailshot and national TV broadcast.
Allied to good polling and targeted mailshots, the techniques Sir Lynton Crosby brought to bear for the Tory's general election campaign, they can generate energy and even excitement.
Both are vying to be named by the Electoral Commission as the officially designated Leave campaign, a status that brings access to £7m in public money and a free mailshot during the crucial final weeks before polling day.
His £3.2m contribution to the Leave.EU campaign – the single biggest individual donation so far – has paid for an anti-EU mailshot to one in three homes in the country.
