Из БОЛ:
When the IDENTITY property is used with CREATE TABLE, Microsoft® SQL Server™ uses the NOT FOR REPLICATION option of CREATE TABLE to override the automatic incrementing of an identity column. Usually, SQL Server assigns each new row inserted in a table a value that is some increment greater than the previous highest value. However, if the new rows are replicated from another data source, the identity values must remain exactly as they were at the data source.
И ещё:

CREATE TABLE (T-SQL)
Creates a new table.
Syntax
CREATE TABLE
[
database_name.[owner].
| owner.
] table_name
(
<column_definition>
...

<column_definition> ::= { column_name data_type }
[ [ DEFAULT constant_expression ]
| [ IDENTITY [(seed, increment ) [NOT FOR REPLICATION] ] ]
]