Not much to go on re the assets you bought but you've got to file form 8594 if you goodwill or going concern value could attach. If you paid $100k for the inventory and no other hard assets then the extra $200k must have been for goodwill or going concern value. Most of this will be entered on your balance sheet with any goodwill being amortized. It seems like you have $300k of additional paid-in capital unless somehow you have an agreement where the corp is going to pay you back for the advance of the $300k to buy the business.
