BigQuery sum counts from start of year to date

I Have a table (TEST_TABLE) which gives me the HEADCOUNT on the last day of each month (LAST_DAY_MONTH) for all individual companies (COMPANNY)

an example for 1 company:

Is there a possibility to create a new table with a summed headcount to date?

i.e

I allready tried

SELECT 
LAST_DAY_MONTH,
COMPANY_NAME,
SUM(CASE WHEN LAST_DAY_MONTH BETWEEN DATE_TRUNC(LAST_DAY_MONTH, year) AND LAST_DAY_MONTH THEN HEADCOUNT END)
FROM `TEST_TABLE`
GROUP BY 1,2

But this just gives the headcount of each month

EDIT:
I ony want to sum headcounts from the same year so if I would look at the row of 2022-12-31, the HEADCOUNT_TO_DATE should be the sum of all 12 months of 2022.

On 2023-01-31 it shoud then only sum the headcount of the first month of 2023

You can use a window function to calculate the running sum of the headcount for each company up to the current row.

SELECT
    LAST_DAY_MONTH,
    COMPANY_NAME,
    SUM(HEADCOUNT) OVER(PARTITION BY COMPANY_NAME ORDER BY LAST_DAY_MONTH) AS HEADCOUNT_TO_DATE
FROM
    TEST_TABLE;

For the same year only you can do:

SELECT
    LAST_DAY_MONTH,
    COMPANY_NAME,
    SUM(HEADCOUNT) OVER(PARTITION BY COMPANY_NAME, EXTRACT(YEAR FROM LAST_DAY_MONTH) ORDER BY LAST_DAY_MONTH) AS HEADCOUNT_TO_DATE
FROM
    TEST_TABLE;

I found the solution, the answer of Asi Salo pointed me in the right direction:

SELECT 
LAST_DAY_MONTH,
COMPANY_NAME,
SUM(HEADCOUNT) OVER(PARTITION BY COMPANY_NAME, EXTRACT(year FROM LAST_DAY_MONTH) ORDER BY EXTRACT(month FROM LAST_DAY_MONTH)) AS HEADCOUNT_TO_DATE
FROM `TEST_TABLE`