An acronym for sub-penny trading; a trading practice where brokers and dealers post orders in dark (invisible) venues and unregulated markets in increments small than a penny (or similar denominations in any currency). Trading may also take place through lit exchanges (lit markets) and wholesale brokers/ dealers. This practice involves undercutting orders in the public limit order book (PLB) by less than one penny, in order to jump the queue of orders in the market (a practice known as queue jumping– QJ).

In essence, sub-penny trading is a form of dark trading whereby traders attempt to undercut displayed liquidity.

It is also known as a sub-penny jumping.