How do I make sure extra income is invested?
That’s what cash-flow priorities are for! In each year, excess income is computed automatically based on your configured income, expenses, debt payments, taxes due, and other variables. What’s left over is saved/invested according to the order of your cash-flow priorities.
Within a plan, you can add cash-flow priorities for existing accounts inherited from Current Finances (or starting conditions, in fixed-date plans), or a variety of new accounts that don’t yet exist. Each type of account comes with its own set of inputs and configuration options. Generally, it’s not a bad idea to have a “Taxable Investments” goal with “maximize contribution” set as the final priority, acting as a catch-all for anything left over after the higher-priority goals in the list.