What does Code A mean in Box 19?

This is the amount of distributions the partnership made to you in cash and marketable securities for things other than performing services. This also doesn't include any deemed distribution of money (which decreases a partner's share of liabilities). If this distribution is more than the value of your basis or investment in the partnership, you need to enter the excess as a sale of stock here: Menu Path: Income > Common Income > Investments and Savings (1099-INT/DIV/B/DA).