I have been purchasing the OPC e-Day Licences for the past 3 years. This time it actually slip my mind and after discovering it, two days have past.
I made an appeal to the Land Transport Authority straight away. This cannot be done through the call centre. It can be done by only emailing to firstname.lastname@example.org or by clicking here>>>
You need to have a valid reason for not paying your e-Day Licence and write to the LTA Officer. Please include your personal and vehicle particulars such as full name, owner identification number, vehicle number, etc. LTA will respond to you and it will take about 1 to 2 weeks.
You will get a call from the LTA Officer and you will need to go to LTA Office at 10 Sin Ming Drive. A letter will be issue to you so that you can purchase the e-Day Licence that you have not bought on the day that you use the OPC Car. LTA responded to me 2 weeks later and I was able to purchase the e-Day Licence that I missed.
Please do not try to ignore the matter and wait until the offence letter comes. The offence letter normally will be sent out 1 or 2 months later. It is best that you are honest and LTA will be able to help you on a case by case basis. There are many cameras on our road network with the ability to read your car plate and the ERP Gantry that you passed through.