Thanks - understand and appreciate the top part of your post. Did not explain myself very well. You are indeed correct with the first line in your second paragraph.
Fair enough. You're unlikely to be able to do it based on NPAT though. NPAT is mostly in companies, and you're operating through a trust.
The way that works is, the trust earns taxable income, but doesn't pay tax. It distributes profits to the family, and they pay tax. So while you can work out what the effective post-tax will be, the trust doesn't really have an NPAT to use. Most schemes similar to this are based on EBIT, not NPAT. EBIT (Earnings before Interest and Tax) is obviously higher (so you may use a lower percentage), but is more linked to the business accomplishments. How you as the owner fund the business (through working capital vs through high levels of borrowings) isn't anything that they can affect. Neither is what rate of tax you pay personally. So saying "this is the profit before interest and tax, you get X of that" is more straightforward than saying "well the business made this, but I financed a bunch of stuff this year, so it's now reduced to that, and then I'll take out 47% for tax".
