For eCom stores without VAT, you can choose to apply discount codes individually or in bulk after VAT. Discount codes are applied excl. VAT by default. Applying a discount code in the form of a percentage after the VAT means that your customer will receive a higher discount. Only apply post-tax discount codes after verifying your regional tax laws.
For European eCom stores, this setting is hidden unless your VAT settings are set to exclude VAT, which is usually only required when selling business to businesses (B2B). This can be enabled in Settings > Taxes > All prices are exclusive of VAT. In North American eCom stores, your eCom store should be set to exclude VAT by default.
In your eCom admin, go to Marketing.
Select Change on the relevant discount code or create a new one.
Turn off the switch labeled Apply discount excl. VAT .