The Belgian social insurance number consists of 8 or 9 digits which are assigned as follows:

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  Digits 1-2 represent the year of birth;

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  Digits 3-4 represent the month of birth;

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  Digits 5-9 are chronologically assigned.

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  The Belgian social insurance number is used to control retirement and survivor claims.

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  The social insurance number is not used for invalidity claims. A separate number is assigned for these claims. If the disabled person dies, the survivor claim is controlled under the widow's own social insurance number.