does anyone know if it is possible to mass delete tax codes?

I just created one and then deleted it. Is your also perhaps being used in a Tax Group? Maybe make your tax code Inactive? What is your observation?

i can inactivate or delete them one at a time but not en masse

might be a job for the scripting channel

yep, ty!

never tried mass delete via script for Tax records but this one does work, worth a look https://netsuite.custhelp.com/app/answers/detail/a_id/79526