This is a list of State Benefits and and the State Retirement Pension is included
https://www.litrg.org.uk/benefits/state-benefits
Some are taxable, some aren’t
The State Pension is taxable, but not at source; that is, it qualifies as gross income and contributes to the tax-free allowance.
There’s been concern recently that the hefty annual increases in the pension in recent times thanks to the ‘triple lock’ will soon lift it above the tax-free allowance threshold due to that having been frozen for several years. So those whose sole income source is the pension will have to pay tax on the surplus above the allowance.
Don’t have a problem with that myself as we oldsters have, generally speaking, enjoyed the best of times and the triple lock on the pension is overly generous (IMO), and in anything more than the short term, unsustainable.
For men born after 1951 and women after 1953 the rise due in April will take the pension to around a grand per month…nice