A severance package is pay and benefits employees receive when they leave employment at a company unwillfully. In addition to their remaining regular pay, it may include some of the following:
Packages are most typically offered for employees who are laid off or retire. Severance pay was instituted to help protect the newly unemployed. Sometimes, they may be offered for those who either resign, regardless of the circumstances, or are fired. Policies for severance packages are often found in a company's employee handbook, and in many countries, they are subject to strict government regulation. Severance contracts often stipulate that employees will not sue the employer for wrongful dismissal or attempt to collect on unemployment benefits, and that if they do so, they must return the severance money.
Severance agreements, among other things, could prevent an employee from working for a competitor and waive any right to pursue a legal claim against the former employer. Also, an employee may be giving up the right to seek unemployment compensation. An employment attorney may be contacted to assist in the evaluation and review of a severance agreement. The payments in some cases will continue only until the former employee has found another job.
In February 2010, a ruling in the Western District of Michigan held that severance pay is not subject to FICA taxes, but it was overturned by the Supreme Court in March 2014.
Employers are required to pay severance pay after an employee working in Puerto Rico is terminated. Employees are not permitted to waive this payment. Severance pay is not required if the employee was terminated with "just cause."
Just cause is satisfied in any of the following situations: the employee had a pattern of improper or disorderly conduct; the employee worked inefficiently, belatedly, negligently, poorly; the employee repeatedly violated the employer's reasonable and written rules; the employer had a full, temporary, or partial closing of operations; the employer had technological or reorganization changes, changes in the nature of the product made, and changes in services rendered; or the employer reduced the number of employees because of an actual or expected decrease in production, sales, or profits.
An employee with less than five years of employment with the employer must receive a severance payment equal to two months of salary, plus an additional one week of salary for each year of employment. An employee with more than five years but less than fifteen years of employment must receive a severance payment equal to three months of salary, plus an additional two weeks of salary for each year of employment. An employee with more than fifteen years of service must receive a severance payment equal to six months of salary, plus an additional three weeks of salary for each year of employment.
Severance agreements are also more than just a "thank you" payment from an employer in Canada. The amount of severance pay an employee is owed when dismissed without misconduct varies between common law (judge-made law) and employment law.
In Ontario, the amount of severance pay under the employment law is given in Ontario by Employment Standards Act (ESA) , which is also explained in Your guide to the Employment Standards Act's Severance pay section . The amount of severance pay under the employment law in Ontario may be calculated using the tool from Ontario Government. It is stated in ESA's Guide Wrongful dismissal section: "The rules under the ESA about termination and severance of employment are minimum requirements. Some employees may have rights under the common law that are greater than the rights to notice of termination (or termination pay) and severance pay under the ESA. An employee may want to sue their former employer in court for wrongful dismissal" .
There is a severance pay online calculator based on "Bardal Factors", to predict the amount of severance pay from court . The goal is to provide enough notice or pay in lieu for the employee to find comparable employment. Unlike statutory minimum notice, the courts will award much more than 8 weeks if warranted by the circumstances, with over 24 months worth of pay in damages possible. Other factors considered may include:
The biggest factor in determining severance is re-employability. If someone is in a field or market where they will have great difficulty finding work, the court will provide more severance. The reason being that the primary purpose of severance is to provide the wrongfully dismissed employee the opportunity to secure other employment within the period provided.   See also Canada section in Wrongful dismissal for related litigation cases in Canada.
In Canadian common law, there is a basic distinction as to dismissals. There are two basic types of dismissals, or terminations: dismissal with cause (Just cause)  and termination without cause. An example of cause would be an employee's behavior which constitutes a fundamental breach of the terms of the employment contract. Where cause exists, the employer can dismiss the employee without providing any notice. If no cause exists yet the employer dismisses without providing lawful notice, then the dismissal is a wrongful dismissal.
There is a time limit of two years from the date of termination for suing the employer in Ontario. This Litigation follows Civil_procedure_in_Canada#Ontario. Before starting a court case, there are other options,  such as, Negotiation, Mediation, and Arbitration.
Typically in a civil lawsuit, in 2019, it can cost $1,500-$5,000 to initiate an action and have a lawyer deliver a Statement of Claim. Responding to the opposing side’s documents and conducting examinations for discovery will likely involve another $3,500-$5,000. The preparation and presentation of your case at trial is likely to add another $5,000—$15,000 to your legal costs.  These legal expense is income tax deductible. 
There are free Legal information and referral services offered on a confidential basis funded from government(The Access to Justice Fund) for all areas of law in major cities, such as, Ottawa Legal Information Centre.
The severance payment in China shall be based on the number of years the employee has worked for the employer at the rate of one month salary for each full year worked. Any period of no less than six months but less than one year shall be counted as one year. The severance payment payable to an employee for any period of less than six months shall be one-half of his/her monthly salary. 
If the monthly salary of an employee is higher than 3 times local average monthly salary where the employer is located, the rate for the severance payment to be paid shall be 3 times local average monthly salary and shall be for no more than 12 years.
Where any employee obtains lump-sum compensation income (including economic compensation, living allowances and other subsidies granted by an employer) from the employer's termination of labor relationship with him/her, the part of the income which is no more than three times the average wage amount of employees in the local area in the previous year shall be exempt from individual income tax.
The fraction of the compensation that exceeds 3 times the local annual average salary shall be taxed as individual income tax as follows For those employees receiving a lump sum compensation, the lump sum can be considered as receiving monthly salaries in one time, and shall be allocated to a certain period in average amount. This average amount will be calculated dividing the lump sum by the service years with the current employer, and will be taxed as monthly salaries. For the number of service years with the current employer, the actual number of years should be considered. If the number of years is more than 12, only 12 will be considered.