The following is extracted from the Guidebook for Employment of Domestic Helpers from Abroad (click here for details) of Immigration Department
--------------------------------------------------------
V. Levy
9. Employers who apply to employ Helpers on or after 1 October 2003 are required to pay an Employees Retraining Levy (levy) in respect of the Helper to be employed to provide funds to train and retrain local workers. The levy payable is HK$400 per month multiplied by the number of months covered by the employment contract. It shall be paid in a lump sum before the issuance of visa or by four equal instalments with the first instalment paid before the issuance of visa.
As far as I know, the visa payment and the collection of visa is done on the same day.
As for me, my agent submitted my application to Immigration Department in December 2003 and the Immigration Department approved my application in January 2004. But I wrote a cheque (payable to HKSAR) to my agent in February and then they took my cheque and the approval letter to Immigration Department to collect the visa.