Zero-Plus Tick

What Is a Zero-Plus Tick?

A zero-plus tick is a tick in which a trade occurs at the same price as the trade before it, and the last change in price was an increase. Markets classify each trade by how its price compares with the previous trade's price. A trade priced above the prior price is an uptick, and a trade priced below it is a downtick. A trade that matches the prior price is a zero tick. A zero tick is labeled zero-plus when the last price change was up, and zero-minus tick when the last price change was down.

How It Works

Consider a stock whose trades print at $20.00, then $20.05, then $20.05 again. The second $20.05 trade follows an upward move, so it is a zero-plus tick. If the next trade also prints at $20.05, it is another zero-plus tick, because the last change in price was still upward. A trade at $20.04 would be a downtick and would reset the classification.

Tick classifications were historically used in rules governing short sale orders. Under the original uptick rule, a short sale could be executed only at a price above the last sale price, or at the last sale price when that price was a zero-plus tick. The goal was to keep short sellers from pushing a falling stock lower.

Why It Matters to Investors

The zero-plus tick is now mostly of historical interest for individual investors. The original uptick rule was removed from U.S. market regulations in 2007. A narrower replacement, which restricts short selling only after a steep one-day price decline, was adopted in 2010 under Regulation SHO. The concept still helps explain how regulators have tried to limit the effect of short selling on falling prices, and how trade-by-trade price data is labeled.