April/May each year
When you start receiving your State Pension
When your LGPS pension increases in line with CPI, your taxable income also rises. HMRC may adjust your tax code accordingly.
The State Pension itself is taxable, but it is paid without tax deducted. HMRC will usually use more of your tax-free allowance against the State Pension, meaning less allowance for your LGPS pension and therefore more tax deducted from it.