As per the he Entry, Exit and Residence (Law No.21 of 2015) an employee can change his job with the endorsement of the government, either on expiry of their agreement, or following five years of  service with the employer, if the agreement is of indefinite term or unlimited period. At present, there is no compelling reason to get a NOC from the past employer for a previous resident to take up another job in Qatar. In case of cancellation of visa or residency permit, the individual can come back to Qatar and take up work promptly on being granted a new visa. The said law abolishes the two-year restriction on expats who wish to return to Qatar on a new employment visa. In this way, an expat who has gotten another contract to work in Qatar can even return to Qatar the next day. 

In case of termination of the employment contract, the employee is given up to 3 months’ time as a grace period to find new job by informing the Ministry of Administrative Development, Labour and Social Affairs. If the employee finds a new job, the person should come back to the Ministry and present the new employment contract. 

If the employee wishes to change the job before their contract period ends or before completion of five years of service, the person should seek permission from current employer.

As indicated by most recent guidelines, if the organization terminates and drops the residency permit of a worker, the individual can come back to Qatar to take up new employment immediately, when they are allowed new visa. The new law abolishes the present two-year ban on  expats, who wish to return to the nation on another visa. An expat with new agreement to work in Qatar can even get back the next day. 

Likewise, the individuals who complete their agreements under the law can come to Qatar the next day of their departure if they get new job offers. Laborers who complete their agreements effectively can get back without facing any ban. 

On the off chance that you have worked in Qatar however at this point you are restricted you can return without NOC on the off chance that you have new idea by another business. New Job offer from new boss that is all you have to returned to Qatar in the event that you are confronting work boycott. This is on the grounds that the new law nullifies 'kafala' or 'sponsorship framework', and subsequently, an individual who had recently worked in Qatar won't need to look for the endorsement of his previous support on the off chance that he is enrolled by another business. 

Previously you have worked in Qatar but currently you are banned, you can come back to Qatar without NOC if you have new offer by a new company. New Job offer from new company that is all you need to come back to Qatar in case you are facing work ban. That is because the new Qatar law abolishes ‘kafala’ or ‘sponsorship system’, and hence, a person who had previously worked in Qatar will not have to seek the approval of his former sponsor if he is recruited by a new company.

In any case, Article 26 stipulates that if an employee is banned as a correctional measure, and he didn't offer his dismissal or oif his plea was rejected by a court, at that point he can't return to Qatar prior to completion of four years.

source: www.onlineqatar.com