Sinn Fein makes £3m a year for election machine
Breakdown of party's finances shows cash flowing into coffers
Sinn Fein has amassed around £3m income across Ireland from various sources, including politicians' salaries, fundraising in America and business interests.
A detailed breakdown of the republican party's finances on both sides of the border has found that it took in £1.1m in Northern Ireland in 2013. That was supplemented by a €2.2m (£1.6m) income in the Republic for its last declared accounts.
But Sinn Fein also generates an estimated €200,000 a year (£145,000) which is ploughed back into the party's vast constituency machine in the Republic, funded by "donations" from the salaries of public representatives who pay themselves an average industrial wage.
American supporters raised around €327,000 (£265,000) for Sinn Fein in the US last year.
Westminster is a significant source of income for Sinn Fein constituencies in Northern Ireland. The party's five MPs claim expenses, but not salaries, as they do not take up their seats. Last year, they claimed £647,047, most of which is invested back in to their constituencies.
This income stream is so important to Sinn Fein that when the rules changed, four Sinn Fein MPs resigned their Assembly seats to concentrate "full time" on Westminster.
If they hadn't done this, then their Westminster expenses entitlement would have been significantly depleted under new rules that penalised double jobbing.
Questions have been asked about how Sinn Fein is spending its Stormont expenses.
A BBC Spotlight programme revealed that Sinn Fein Assembly members drew down £700,000 in expenses, which was used to pay for "research" done by a company run by Sinn Fein.
The investigation found that over a 10-year period, 36 different Sinn Fein MLAs claimed about £700,000 in total through Stormont expenses to pay Research Services Ireland.
Deputy First Minister Martin McGuinness alone claimed £42,000 over 10 years for the expertise of the company. Speaking at the time of the claims, Sinn Fein MLA Raymond McCartney said there had been "no impropriety" in his party's expenses claims and added they had "nothing to hide".
"I have no issue with any investigative process, indeed the Spotlight programme alluded that some time in the past the PSNI had been involved," he said.
"They didn't find anything to proceed with an investigative process, I can draw a conclusion from that there was no evidence to go by."
The funds in Northern Ireland are in addition to parliamentary expenses that public representatives can claim against their constituency offices and other spending in the south.
Sinn Fein TDs claimed €7m (£5m) over the four-year life of the current Irish government - an average of €500,000 (£362,000) per TD.
The party makes a virtue out of drawing the minimum wage, however the benefit is not to the taxpayer, but its constituency machine. The "average industrial wage" rule means that salaried public representatives have to relinquish up to a third of their salaries to their constituencies.
The rule also applies in Northern Ireland, where the party's 29 MLAs draw an average industrial wage of around £26,000 from salaries ranging from £48,000 to £120,000, with the surplus paid into the local party machine.
Meanwhile, the party's assets in the Republic include two companies, Parnell Publishing and Republican Merchandising. The first publishes the party's newspaper An Phoblacht. Sinn Fein owns at least three properties, two in Dublin's Parnell Square and at least one in Belfast worth around £71,000.
One advantage over its rivals is that Sinn Fein is the only Irish or British party that raises funds in the US.
In America, Friends of Sinn Fein raised £237,236 in the year to November last year, or a massive £3.5m over the past decade, according to figures which were released by the US Department of Justice.