Starting in 2015, the participant timestamp is available alongside the primary timestamp in TAQ data. This paper shows that all trades and quote updates triggered in the execution of the same marketable order receive the same participant timestamp. Making use of this insight can greatly improve TAQ data. The insight is applied to gauge the prevalence of sequence errors in TAQ data, to accurately obtain otherwise biased prevailing NBBO prices and depths, to improve trade signing, to discern the size of marketable orders, and to identify executions against hidden liquidity directly in TAQ data.