How an annual management fee is worked out

Our fee is a percentage of the value we look after, worked out at the end of each month and taken from the cash part of the portfolio.
On a $400,000 portfolio at 0.90% a year, that is about $300 a month, or $3,600 a year. The funds we buy have their own costs, about 0.20% a year or $800 on the same portfolio, and we show those on every statement too (example prices).
If the portfolio grows, the fee in dollars grows with it; if it falls, so does the fee.