(1) If you are an investment adviser registered or required to be registered pursuant to RCW
21.20.040, it is unlawful under RCW
21.20.020 for you to provide investment advice to clients unless you deliver written billing information to your advisory clients each time you charge an advisory fee. The written billing information must include the fee(s) charged, the formula used to calculate the fee(s), the fee calculation itself, the amount of assets under management the fee is based on, and the time period covered by the fee(s). If you charge performance compensation, the written billing information must also include the client's cumulative net investment gain (or loss) and the amount of cumulative net investment gain over which you will receive performance compensation. You must include the name of the custodian(s) on the fee invoice.