Mr Green is due to leave the group when the merger is complete after being ousted as chairman of the new ITV plc in October by institutional investors led by Fidelity Investments.
News of the pay-off is understood to be included in the listing particulars for the merger.
The payment is the equivalent of two years' salary Mr Green was paid £707,000 in 2002.
In addition, he will also receive two years' pension contributions, and walk away with millions of pounds worth of share options.
Mr Green, who founded Carlton more than 20 years ago, has never had a formal contract with the media group.
However, the group is understood to have been given legal advice, saying that after working for the firm and drawing a salary for a number of years he has an implicit contract, and should be treated in the same way as other directors who have two-year contracts.
But the move is likely to spark outrage among shareholders who called for the removal of Mr Green, who is held partly responsible for the collapse of ITV Digital, and demanded the appointment of someone from outside the two groups.
Carlton is also understood to be giving finance director Paul Murray a pay-off of several hundred thousand pounds when he leaves.
Tomorrow's listing particulars will also include details on Charles Allen's contract when he takes over as chief executive of the new group.
It is thought his current two-year contract at Granada will be reduced to an annual contract when the £4.5 billion merger is completed in early February.
Last month the two companies signalled there would be job cuts when they announced the combined group would make cost savings of about £100 million.
The merger was approved by Trade and Industry Secretary Patricia Hewitt. She accepted undertakings relating to "behavioural remedies" to address their dominant position.