Regarding EPF contributions, they are limited to the monthly threshold salary of the employee. If an employee receives double wages for working on a national or festival holiday in a month, this additional amount automatically combines with the gross salary for that month. It then becomes part of the contribution due for that month, within the set threshold limit.
In the case of ESI, any extra wages paid for national or festival holidays are included in the total contribution amount for that month, as these wages are paid alongside the regular monthly wages.