NS&I has also taken the controversial decision to cut the rate further to 2.15% from November. 'It's the flight to safety,' an NS&I spokeswoman said, explaining the popularity of premium bonds. 'People like the security and the excitement.' Prizes are tax-free so the effective current return is higher at 2.81% for a basic-rate taxpayer and 3.75% for a higher-rate taxpayer, she said.