A hospital trust in London is predicting a private income of more than £100m in 2018-19.
The Royal Marsden Foundation Trust is planning on a private care income of £110m next financial year. It also anticipates income of more than £100m this year for the first time, after the division performed better than expected.
If achieved, the 2017-18 total would be a 12 per cent increase on the previous year.
The 2018-19 target is a 7 per cent increase on what was planned this year.
Board papers due to be presented this week acknowledge there are risks around delayed payments from debtors and an increase in patients referred from foreign embassies, who have often paid late.
Another report also said the trust had managed to get its private care debtors beneath £30m in January.
The trust is considering business cases for additional private robotic surgery and MRI work. The specialist cancer trust is based in Chelsea but operates community facilities in Sutton in outer London. Last year, the board approved the development of a new facility at Cavendish Square in the West End.
Two-thirds of the 2018-19 projected income for the trust is likely to come from private patients, the highest proportion of any NHS trust in England.
Great Ormond Street Hospital for Children FT also performs large amounts of private work and has identified late payers as a significant risk.
In December, the most recent available figures, it was owed £24.7m by international private patients.
The Health and Social Care Act 2012 raised the total proportion of income an NHS trust could earn privately to 49 per cent.