P began selling merchandise to D or her corporation in December 1987. P did not conduct any credit investigation. It did not inquire or, insofar as appears from the evidence, think about, whether its customer was an individual or a corporation. P sold the first six or seven orders for cash on delivery. Later orders were directed to 'Ecco Bella' at P's home address and shipped on fifteen days' credit. Ecco Bella's name was substituted, without any indication that it was a corporation. Merchandise delivered went unpaid on one of the bills. P sued D personally. P addressed its bill for the purchase price to 'Ecco Bella.' P received payment for prior orders by checks imprinted with the name 'Ecco Bella.' D's company's letterhead also read 'Ecco Bella.' Neither the checks nor the letterhead carried the name 'Ecco Bella Incorporated' or otherwise indicated that Ecco Bella was a corporation. P's sales manager testified, without contradiction, that no one had told him Ecco Bella was a corporation and he did not know that it was. The trial judge held that D's failure to affirmatively disclose the corporate status of her company led P to believe that it was a sole proprietorship. Since it had not filed a trade name certificate, the judge ruled that D was personally liable for P's unpaid bill, and he entered judgment for $1530. D appealed. P cross-appealed for prejudgment interest.