There are provisions in Qatar Labor Law that forfeits the gratuity entitlements for specific reasons as stated in the law. Generally, there should be no difference in computing the gratuity as it is based on your employment contract (no. of days entitled).

Notice period is required except when you are still on probation. However, company may opt to pay you for the notice period and terminate immediately.

Please note that you need to review your contract and company policies as well.