In the old days you had to buy an annuity by age 75 but nowadays with Pension Freedoms you dont have to do anything at age but there are a few things to watch out for:
1 Some pension plans will require you take your benefits (annuity, cash or drawdown) by age 75 or else transfer to a new pension plan
2 The tax postion changes for death benefits - your beneficaries will pay tax on any money taken out of their share of the pension
However, even though you dont have to do anything and you could just leave your pension pot to grow there are some good reasons why you should consider taking cash and income from your pension when you get to age 75