You can find your DP ID and Client ID in the profile section of your broking account.
If your DEMAT is with CDSL, both the DP ID and Client ID will be eight digits each. For example: If 0577057744224422 is the Demat number/ID, then DP ID is 05770577 and Client ID 44224422.
If your DEMAT is with NSDL - both DP ID and Client ID will be of 8 characters each where the starting characters are ‘IN,’ and the following characters will be numeric. For example: If IN12345678912345 is the Demat number/ID, then DP ID is IN123456 and Client ID 78912345.
Alternately, you will find your DP ID and Client ID in your E-CAS statements that are sent to your email id associated with your broking account.