The group, which has nearly 400 stores and owns brands including Slazenger, Donnay and Karrimor, said retail sales rose 10.2% to £408.6m in the 13 weeks to January 22, boosted by strong growth in internet trading.
It is now "certain" of hitting a bonus trigger of underlying profits of £225m for the year to April under the first leg of a three-year reward programme for Mr Ashley, who is executive deputy chairman.
Mr Ashley, who netted £929m in February 2007 after selling 43% of the business he founded, receives no pay but is now on course to receive six million shares, currently worth £16 million, in 2018.
The bonus that Mr Ashley could be in line to pocket has increased by £4m in recent months, reflecting the company’s improving performance on the stock market.
Hitting a lower target of £215m will also be a key milestone in the chain’s staff bonus scheme, which last year paid out more than £40,000 on average to some 2,000 staff.
It is thought to be the largest windfall handed out to shop staff in Britain and has been a large factor in the chain’s strong performance in recent years.
Under the terms of a new scheme introduced last year the company needs to hit targets for four years to trigger a further pay-out.
Gross profits increased 10.2% to £184.4m as trading since December was better than it expected and has remained strong since the end of January.