Does Kalshi send a 1099?

Yes. Kalshi issues 1099-B forms to US users because it is a CFTC-regulated designated contract market. Kalshi contracts may qualify for Section 1256 tax treatment, which gives a favorable 60/40 split: 60% of gains taxed at long-term capital gains rates and 40% at short-term rates, regardless of how long you held the position. This can result in a lower effective tax rate compared to all-short-term treatment.