Sage 50 Accounts

This has just come to my attention after 30 years of Sage use (admittedly intermittent) When the client has the override tax code turned on, it does not affect the tax code of Special Stock Codes S1, S2, S3. This is nonsensical and results in errors…

I'm sure this must be possible, but I can't find the option anywhere - I've only seen how to set the Tax codes for these. Thanks in advance