Hi Rodolphe ,
Apologies for any inconvenience caused, and thanks for your feedback.
We didn't realize that tax rates can have one or more decimals. We'll change this for the next ATUM version to allow decimals.
FYI, this field is only added for information purposes. It isn't used anywhere in ATUM Free (we use it in Purchase Orders Pro).
Best Regards,
José Andrés