USCIS is not currently accepting H-1B petitions for the fiscal 2005 (additional 20,000 H-1B numbers) where the petitions request only start dates prior to 10/1/05. Further any petitions with filed now with employment start date earlier than 10/1/05 will be rejected by the Service Centers.

However USCIS will not reject an H-1B petition if there is an annotation requesting USCIS to issue an earlier start date if and when the additional 20,000 numbers are available. USCIS HQ official also indicated that there is no guarantee that this approach will be of any particular assistance in securing one of the fiscal 2005 numbers. USCIS is unwilling to say more on the subject.

Source (AILA – April 19, 2005