How is tax calculated per monthly wage?

The rates are here https://ird.gov.mt/services/taxrates.aspx and social security here https://ird.gov.mt/services/sscrates.aspx

The social security is per week, a month has as many weeks as it has mondays.  So for this purpose November 2016 has 4 weeks and October 2016 has 5.

It's a pain to follow these numbers but you should be able to align it up with your payslip and the payslip must state which social security band they used to calculate - like D or whatever.

NOTE: There might be differences based on your type of employment, I am not sure, this is how I calculate/verify the ones for my staff that I get from accountants - this being based on fixed annual incomes.  With variable incomes, you'll probably get different results every month

Thank you volcano. I understand that one if calculated annually. I already emailed our accountant and hope she can enlighten me on this one. The previous month I was only deducted of not more than 300 euro, this month I received almost the same amount from the previous wage but Now I'm was deducted 500euro.

If your income is not set, you probably entered a new tax bracket now, but yes, best to ask your accounts/HR