MATERNITY BENEFIT SSS INITIAL PAYMENT 50%

Hi. I need legal advise. I am 32 weeks pregnant for my second son. I have notified my employer last Jan 5 about my pregnancy (MAT1), they told me that they (my employer) will be the one who will file it for me since I'm pregnant. They also told me to come back the following week so they can give me the copy of the MAT1 which I will keep till I gave birth for MAT2.
They told me that they will only give me half (50%) of my maternity benefit and the rest (50%) will be given after the completion of MAT 2.
The reason for this, and I am quoting my companies HR... is because some employee do not come back to the company i.e. quit, resign, or job abandonment and the past employees do not file the Mat2, and it is in the desecration of the company to give 50% or 100%, stated by their HR Representative of Compensation and Benefits. My question is....

Is it illegal for them to just give me 50% (half) of the monetary benefit from sss? Or do they have to give 100% by law?

When I gave birth to my 1st son I was working for different company and they gave me the whole (100%) benefits through my
atm payroll acct.

If this is illegal, could you tell me the Republic Act # (number) and what section? So that I can show proof to my employer and HR.

Thank you for your time,

it's supposed to be 100%. make a courteous letter to question their basis for doing so. make sure you retain a copy with proof of receipt. hint that you intend to go to sss to get an opinion.