"I did more digging at looks like Baxter was at $29.13 on Dec 1st, 2001. I had 1,152 shares of Baxalta sold in the merger, so $29.13 X 1,152= $33,557.76 should be my cost basis, correct?"
I wouldn't think so, no. 12/1/2001 was a Saturday so not a trade or settlement date. The 11/30/2001 H/L/C for Baxter were $28.36 $27.95 $28.25
But Baxalta was spun off from Baxter which means you need to allocate your Baxter basis between Baxter and Baxalta;
44.8 % to Baxalta and 55.2% to Baxter. You can't take whatever price you paid for Baxter and apply all of that to Baxalta.
"$53,180 in proceeds sent to IRS"
Not sure why your proceeds and the broker's proceeds are so different - you may want to ask - but I'd think you would need to use the broker's figure.
