The person who claims the ticket and pays it to the others will fill out form 5754 and turn it in to the lotto commission or other payer of the prize when the prize is claimed. The payer will use it to issue W-2G forms to each winner. If it wasn't split up front then you can still claim only your portion and attach a statement to the return showing the information and allocations to each person. It's better to split it when the ticket is originally cashed as you are relying on the other members of your group claiming their portion otherwise you can find yourself in a mess with the IRS. It's probably best to seek advise from a professional.
