Are you permanent staff with the company? If yes, the company should do PCB from your salary. Unless there is some agreement that employee pays their own tax but this is usually for freelance worker.

You didn't notice in your monthly payslip?

Not much to go around it, as it means you have received the salary without PCB deduction. So as employee, have to make the payment to LHDN, so it is no longer the issue with the company.

Few years ago I also had this problem. For several payment the company didn't make PCB, so in the end I had to pay up. What I do is fill in the e-filing as normal and the system will tell how much to pay. From there request for monthly payment instead of lump-sum payment - I forgot the exact way but there was.

It can be declared in e-filing. You just fill in all the details in e-filing and at the end it will show you how much you have to pay. Better that way, in my opinion, rather than pay first before filling in e-filing as you will know exact amount to pay after all deduction and tax relief.