Once you reach the legal retirement age (age 55, rising to 57 in 2028 in the UK), you can technically access your entire pension pot, but cashing it out in one full lump sum is rarely recommended. Under standard rules, only the first 25% is tax-free, while the remaining 75% is added to your taxable income for that year, which can push you into a higher tax bracket and trigger a massive, avoidable tax bill.