Did not make up missed fasts before arrival of following Ramadhaan due to laziness

A 45 year old man has not fasted during the month of Ramahdaan for many years out of laziness and negligence, and nor has he made up any of the missed fasts over these years. However, Allaah (Subhaanahu wa Ta’aala) has [now] bestowed upon him the opportunity to repent and he has started fasting the month of Ramadhaan after the passing of ten days. So what is the ruling regarding the previous days, the months of which the number exceeds ten?