What is your concern?
Can you point out to me where in the labor code that said employers are mandated to give payslips?
I agree with the need to give employees payslip but there is nothing in the labor code stating or mandating employers to give payslip to employees, so the employer is not violating anything.
Do you suspect the employer is shortchanging you?? like not paying SSS, PHIC or Pag-ibig benefit / contributions?? if there are you can report them to the nearest DOLE office.
Btw, it is not a good practice for you to sign cash vouchers with no content. This might be used against you in the future. in example, if you signed a blank cash voucher, someone might write CA of Pxx,xxx.xx for this event. Then you might find yourself being sued for non-liquidation of cash advances. I'm not saying that your company will do that to you, I'm just stating that it is not a good practice to do that.
Hope this helps.