In the couple's divorce battle, Mr Justice Bennett ruled that was the total of Macca's fortune. But Heather disagrees.
'We all know he's worth £800 million. He's been worth £800 million for the last 15 years,' Heather said outside the High Court after the judgment was announced.
Heather, 40, was awarded a £24.3m settlement. But she hopes that showing Sir Paul is worth more will lead to a higher payout for her and their daughter Beatrice, 4, who will receive £35,000 a year maintenance.
'Heather says she can prove the amount of money that is being given to look after Bea will not last over the year,' a source tells the Daily Mail. 'She's keeping every receipt to show that £35,000 is just not sufficient.
'Heather is hoping Paul will discretely make a payment to her annually rather than go back to court and rake all this up again.'
Get more celeb news from Now Magazine