The short answer is May 2011. However, many mailers find it makes good business sense to begin using the Intelligent Mail Barcode now, even though you can continue to use the POSTNET barcode on mailings that qualify for automation discount postage rates through April of 2011. Beginning in May 2011, you'll have to use the Intelligent Mail Barcode on those mailings.
Mailers can use the Intelligent Mail Barcode today to select a range of USPS services including OneCode Confirm for tracking and OneCode ACS for change of address updates. Later this year mailers will be able to get an addtional discount off barcoded First-Class and Standard mailpieces if they use the Full Service option.
It also makes sense to get started sooner, so that you can work with your postal acceptance specialist at the post office where you enter your mail to ensure your barcodes are readable and formatted correctly.
