The parties put under the scanner are the BJP, CPM, CPI, BSP and the NCP, based on the income tax returns submitted to the Election Commission of India. The Congress, according to ADR, has not submitted its audit report to the commission yet.
The BJP and the NCP submitted their records to the commission several days after expiry of the November 30 deadline, the watchdog said.
Among the five parties, the NCP is the only one to make public details of all voluntary contributions.
In the case of the BJP - which had the highest income in the year under review - the source of 50 per cent of voluntary contributions to the party is unknown.
"Unknown sources" is a term used when income from donations under Rs 20,000 is declared in the tax returns without mentioning the source. This could cover sale of coupons, relief fund, miscellaneous income, voluntary contributions, and contribution from meetings and morchas.
The BJP's income for the year was Rs 970.43 crore, with the CPM coming a distant second at Rs 123.92 crore. The BSP's income was Rs 111.95 crore, the NCP's Rs 67.64 crore and CPI's Rs 1.84 crore. The BJP accounted for 76.06 per cent of the total income of national parties.
While the BJP leads the parties in total income, it is the BSP that has registered the biggest increase in income. As against BJP's increase in income by 44.02 per cent, the BSP's jump over the previous year was 67.31 per cent.