Regarding Certificate of practice

Dear Sir,

This query is with regard to Relieving Letter from previous employer, which is required during applying for Certificate of practice

My sister was employed with a firm as a Tax consultant for 8 months before leaving it. Since last 5 months the Employer is not providing with requisite Relieving Letter. repetive efforts have failed to acquire and the employer has refused to provide with it.

Is there any substitute to the above situation. or how can she go about it for obtaining the certificate of practice without the relieving letter.