What does "Display size is not supported for OTCBB stocks" mean?

The order rejection "Error 503" message is displayed when your account does not have trading permissions for the product you are trying to trade.

Additional Information…

When you see the message "No opening trades: ineligible PINK stock" it means an opening order for that contract is not allowed, even if your account has trading permissions for US Penny Stocks.

Additional Information…

The maximum order size for stocks is 500,000 shares.

IBKR does not have a maximum order size for most other products, but you are limited to the amount of cash or margin in your account…

To create or edit an Iceberg order in Mosaic first click on "Advanced" in the Order Entry window. Click in the "Iceberg --" field and enter a value (amounts for stock orders should be in 100 share round lot increments) into the field provided. Click Enter on your keyboard to submit the value. This value will serve as the size increment of the amount displayed for your order…