Age-related limits - when is your age determined

Hi.
If I am 49 at the start of 2021 and 50 at the end of 2021, can I claim tax relief on up to 30% of my pension contributions or only up to 25% of the contributions?
I.e. is my age at the beginning or the end of the tax year used to determine my age-related ceiling?

It’s the age you turn during that year.

So if you turn 50 during 2021, it’s 30% for 2021.