Is leave lapses if not taken more than 4 years as per qatar labor law

Article 75

...If the circumstances of the work necessitate the

employment of the worker during the rest day the worker shall ... be paid for working that day the wage payable to him for the ordinary rest day or his basic wage plus an increase of not less than 150%.

note that if you didn't take the leave days because your employer wanted you to work, than they are counted as extra additional work day so you get >150%

so the calculation will be

basic/30 * 100 * 1.5

basic/30 is your mean daily income

100 leave days untaken

1.5 is the 50 % bonus for extra work.

Thanks

if you have 100 untaken leave days, you should be compensated with:

basic salary / 30 * 100

Article 81

...The worker shall be entitled to payment in lieu of his annual leave equivalent to his wage for the leave days to which he is entitled ...