Illinois employers are not required to recognize holidays nor pay their employees on holidays not worked, unless there has been a prior contract or agreement established. Employers may choose to remain open during holidays, in which case they would pay their employees a normal rate of pay (with the option of any special holiday pay) and observe any overtime rules that may apply.
Employers are required to pay their employees at least semi‑monthly, and to pay every employee all wages earned during the semi‑monthly pay period. Wages earned by employees during a semi‑monthly or bi‑weekly pay period must also be paid no later than 13 days after the end of the pay period in which such wages were earned, unless there has been a valid collective bargaining agreement which provides for a different date or for different arrangements for the payment of wages.
If an employee quits or is fired, they are not entitled to any future holiday pay (for days that have not already occurred) but they are entitled to payment for any unused accrued vacation time. They are not, however, required to pay severance pay, sick pay or holiday pay upon separation, unless it’s been stipulated by employment contract or agreement.
Although employers in Illinois are not required to observe holidays, some do recognize days such as Christmas and New Year’s Day, but even in that case, they are not required to pay their employees if the business is closed and/or the employee is not scheduled to work. Offering holidays off and/or paying employees for holidays not worked are benefits and are above and beyond the Illinois labor laws and completely up to the discretion of the employer (unless those items are terms of a collective bargaining agreement or a contract between the employee and employer).
The Illinois Complete Labor Law poster contains all of teh most up to date labor laws for Illinois as well as the federal laws.