Bostock's pension allowance - which was worth 588,000 pounds ($754,404.00) last year - will be reduced from 35% of his base pay to 22% in 2020 and to 9% in 2021, a source familiar with the matter said. That will equate to a cut of more than 400,000 pounds over the two years.
He received a total pay package worth 6.4 million pounds in 2018, including a final 1.8 million pound payment for share awards he gave up when he left Royal Bank of Scotland in 2013.
Santander's move comes as rivals including HSBC and RBS have already cut executive pension perks this year to meet corporate governance guidelines, while others including Barclays and Lloyds have plans to do so.
Details of Santander UK's planned cuts were first reported by The Financial Times.
(Reporting by Iain Withers; editing by Mike Harrison)