In column K both overtime pays are not multiplied by their loading.

At first I was like, whaaat, but then I was like OH DUH

But I'm not 100% sure on how to get them to multiply correctly, since feeding in a formula of "=multiply(H8, H10, 2)" provides the error "Expected two arguments, got three arguments". It must be possible to multiply all three variables within the program in an efficient way, but how?

Tax rates are progressive - the first $x you pay no tax, the next $y you pay z%... so your tax calculations are incorrect.

I knew this seemed off, but I'm completely baffled as to how to include that kind of tiered calculation in my spreadsheet. Suggestions or tutorial materials?

Your yearly calculations are also incorrect, as there are not 52 weeks in a year - that would make a year 364 days, and you do not work 52x5 days per year as there are public holidays and annual leave.

So, 365/7 = 52.142857, more accurate?

Not everyone has paid holidays off, or annual leave. Also, not everyone works full time... How could I incorporate these as a variable?

Also, you work overtime, so does any involve extra commutes (e.g. working weekends).

I don't work weekends, so for me it is only 5 days. But it might be a good idea to include a little box that says something like.... "# Days Per Wk Commuting"?

If anybody can point me to a good online class or tutorial that would teach me some of these more complicated bits, that would be just awesome. In the meantime, I suppose I'll just keep messing around with it!