There’s an additional step you may need to take which is not discussed in the PortfolioCenter documentation for dealing with the bifurcation of average cost mutual funds.
If you plan to switch from average cost accounting long term, you should change your PortfolioCenter Defaults so that new accounts are created using FIFO (or your new chosen method).
Every new account needs to be populated with the correct data fields to match your choices. You can make your life easier by choosing which default details are automatically applied to new accounts.
If you are switching your matching method from average cost accounting long term, you should update your Portfolio Defaults to your new choice. And of course, make sure your broker is aware you plan to switch long-term. Otherwise the cost basis of your new accounts will fail to reconcile with your broker.
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