The USP identification tests by HPLC retention time indicate that the retention time corresponds to that exhibited by the Standard. Is there a generally accepted definition of "corresponds"?

Usually within 1% of standard's retention time.

Is there any document to which we can make reference for this practice? Ussually, during an audit, the question for references of acceptance criteria arises.

where does this 1% limit comes from? If Std injection followed by say some 10 sample injections, there is always a possibility that last injections may not meet that 1% criteria but still if the sample contains only one active we can never reject the result only on the basis of RT.
In these kind of cases whether there is any pharmacopeial/regulatory guidance available?