The number of higher-rate income taxpayers could double to around two-thirds of all taxpayers by the 2075/6 tax year, according to analysis from the Office for Budgetary Responsibility.
Assuming the National Living Wage remains constant as a share of the median wage, a full-time National Living Wage earner would also become subject to the higher rate of income tax (40%) from the late 2060s.
About 7m people are currently believed to be higher-rate taxpayers but this figure will rise sharply over the next 50 years, according to the OBR.
Another area expected to skyrocket for the Government is Inheritance Tax receipts. The OBR predicts IHT revenues will double from 0.4% of GDP in 2030 to 0.9% of GDP by 2075.
The OBR data also highlighted the ongoing effects of increasing longevity. In its baseline scenario, it predicted that the median age will rise from 40 to 49 by 2075, with the modal age (the most common age) jumping from 34 to 63.
Life expectancy growth is however expected to slow, with average life expectancy of 86.5 years by 2075 (2025: 81.5 years), a slightly lower increase than over the past 50 years.
Despite the slowing in life expectancy, the old-age dependency ratio is set to reach 40% by 2075. The ratio compares the proportion of the population at or above the pension age in relation to the rest of the adult population. This is a considerable increase to the ratio which has held steady since the 1970s at around 30%.
Perhaps unsurprisingly this is expected to place considerable pressure on the State Pension, says OBR, which predicts the State Pensions will increase from 5% of GDP by 2030 and to 9% by 2075. This assumes that the State Pension Triple Lock is maintained.
The OBR also noted that it expects an increasing number of those reaching retirement age to continue working. Among 65 to 69 year olds it expects the participation rate to increase from under 30% in 2025 to 45% by the mid-2040s, with the participation rate for over 70s rising from 7% to 10%.
• OBR Report: Fiscal Risks and Sustainability - July 2026.