How is Full-Year National Insurance Contribution Determined?

Could you please advise how a full year of National Insurance (NI) contributions is calculated? Is it assessed on a month-by-month basis, or is it averaged across the entire tax year? For example, if my contractual annual salary is £60,000, and after 8 months into the tax year, I decide to increase my salary sacrifice for workplace pension contributions to 100% of my salary for the remaining 4 months, my income for the last 4 months of the year would be £0. However, my total salary after sacrifice for the full tax year would still amount to £24,000, with the respective NI contributions deducted during the first 8 months. In this scenario, would the year still count as a full NI contribution year? Does it have any negative impact on my future state pension?

Hi,
A qualifying year is determined on weeks, if based on a credit.
For example, you would have a full qualifying year if a National Insurance credit (Child Benefit, Universal Credit etc) covered the full period of the 6th of April until the 5th of April. However, in terms of employment it is based on the annual income and can differ in each tax year.
For the current tax year 2024/25, the earnings threshold for a full qualifying year is £6396.00.
Therefore, in your scenario a salary of £24,000 in the tax year would provide a full qualifying year for National Insurance purposes. 
Thank you.