JTD is jaar tot datum.
YTD is the english for that.
Jaar/Year refers to the financial year. i.e. Mar of one year to Feb of the next.
About his hours, he should refer to his contract of employment to determine his hourly rate. He should then request time sheets for his hours worked. And he should reconcile the two. And his gross salary should be the result.
About the bonus tax, I havent seen it before, but it isnt a bad idea. I would say that more companies should do this for their staff. That couple of hundred rand less every month psychologically isnt going to bring you as much joy as receiving the cumulative benefit with your December pay cheque. If you really strict about you finances then take the benefit monthly. But for most people that extra cash will just get included in cash flow.
And the interest on say R10 000 is like R400 per year. That is if the R10 000 is invested for a full twelve months assuming you get an interest rate of 4%. So with say R800 monthly contributing to your bonus tax total, the interest on that would be musch less. To pay R10 000 tax, your bonus would have to be like R40k. In which case that R100 to R400 doesnt actually bother you. The other thing is you only earn interest in a savings account. Most people have cheque accounts and dont bother transferring funds (or atleast such small amounts) to their savings account.
It is pointless looking at one payslip in a vacuum. What few people do, and I personally think more people should do, is reconcile their irp5s with their payslips. Because an irp5 basically is a summary of your incomes and deductions from a particular employer.
I have seen it before where the irp5 and payslips dont match. Particularly with the PAYE paid. I suggest to first always enquire from the employer if you unsure about anything. Normal people draw up irp5s. Human errors do happen. Because you might think you are being screwed over and report malpractice to SARS AND MAKE A BIG HOOHAA, only to find out that your stuff is actually worked out correctly. So do your homework first. Consult someone with knowledge on these things if you must. You dont want to feel like an idiot later everytime you see your boss.
AND MAY THE FORCE BE WITH YOU.