A * general insurance company's assessable income for the * current year includes an amount equal to the amount (if any) by which:
(a) the value, at the end of the previous income year, of the company's adjusted * liability for incurred claims under * general insurance policies; exceeds
(b) the value, at the end of the current year, of that liability.
Note: Those values are worked out under section 321 - 20.