Mr Pemberton sold the stock on March 20 at $1.36 per share.
NRW’s shares close 5 cents higher today at $1.20.
They traded as low as $1.10 earlier this month after briefly touching an eight-year high of $3.40 in January.
The company said Mr Pemberton’s tax liabilities were directly linked to the award of shares from the company’s long-term incentive plan.
The trades were completed shortly after the lifting of a share trading restriction linked to the acquisition of BGC Contracting, the associated equity raise and contract announcements made last week.