Customizing tax classes

protected virtual TaxClassInfo GetTaxClassInfoInternal(int classId) { }
protected virtual TaxClassInfo GetTaxClassInfoInternal(string className, string siteName) { }

protected virtual void SetTaxClassInfoInternal(TaxClassInfo classObj) { }

protected virtual void DeleteTaxClassInfoInternal(TaxClassInfo classObj) { }

protected virtual ObjectQuery<TaxClassInfo> GetTaxClassesInternal(int siteId) { }

protected virtual ObjectQuery<TaxClassInfo> GetSKUTaxClassesInternal(int skuId) { }

protected virtual ObjectQuery<TaxClassInfo> GetDepartmentTaxClassesInternal(int departmentId) { }

protected virtual DataSet GetTaxesInternal(int skuId, int countryId, int stateId, string zipCode) { }
protected virtual DataSet GetTaxesInternal(ShoppingCartInfo cart) { }
protected virtual List<IItemTax> GetTaxesInternal(ShoppingCartItemInfo item) { }

protected virtual double GetTaxValueInternal(double price, double taxValue) { }

protected virtual double ApplyTaxInternal(double price, double taxValue) { }

protected virtual DataSet GetShippingTaxesInternal(ShoppingCartInfo cart) { }

protected virtual int GetSKUIDToGetTaxesInternal(ShoppingCartItemInfo item) { }

protected virtual IItemTax GetItemTaxClassInternal(DataRow dr) { }

using System.Data;

using CMS;
using CMS.Ecommerce;

[assembly: RegisterCustomProvider(typeof(CustomTaxClassInfoProvider))]
public class CustomTaxClassInfoProvider : TaxClassInfoProvider
{
    /// <summary>
    /// Returns a set of taxes that are applied to the provided shopping cart items.
    /// Assigns taxes based on the items' departments.
    /// </summary>
    /// <param name="cart">Shopping cart with products to be taxed.</param>
    /// <returns>Shopping cart items' tax class dataset.</returns>
    protected override DataSet GetTaxesInternal(ShoppingCartInfo cart)
    {
        // Creates a new dataset for taxes
        DataSet ds = new DataSet();

        // Creates a new empty table for taxes
        DataTable table = GetNewTaxesTable();

        // Loops through all items in the shopping cart
        foreach (ShoppingCartItemInfo item in cart.CartItems)
        {
            // Note: You can replace the 'foreach' content with your custom logic of tax calculation.

            // Does not add any taxes to products without a department assigned
            if (item.SKU.SKUDepartmentID > 0)
            {
                // Gets the product's department to make a decision about the tax amount
                DepartmentInfo department = DepartmentInfoProvider.GetDepartmentInfo(item.SKU.SKUDepartmentID);

                // Gets the product's ID to know which product has which tax (for variants, gets the parent's ID)
                int skuId = item.SKU.IsProductVariant ? item.SKU.SKUParentSKUID : item.SKUID;

                // Assigns a tax based on the product's department
                switch (department.DepartmentName)
                {
                    // Adds a 20% tax to products from a department with a name "Coffees"
                    case "Coffees":
                        AddTaxRow(table, skuId, "Tax " + department.DepartmentDisplayName, 20);
                        break;

                    // Adds 11% and 10% taxes to products from a department with a name "Grinders"
                    case "Grinders":
                        AddTaxRow(table, skuId, "Tax " + department.DepartmentDisplayName + " 1", 11);
                        AddTaxRow(table, skuId, "Tax " + department.DepartmentDisplayName + " 2", 10);
                        break;

                    // Adds a 0% tax to products from a department with a name "Brewers" (i.e. does not add any taxes)
                    case "Brewers":
                        break;

                    // Adds a 5% tax to all other departments
                    default:
                        AddTaxRow(table, skuId, "Tax " + department.DepartmentDisplayName, 5);
                        break;
                }
            }
        }

        // Returns a built dataset with the taxes
        ds.Tables.Add(table);
        return ds;
    }

    /// <summary>
    /// Creates an empty tax table.
    /// </summary>
    /// <returns>Created empty table with predefined columns.</returns>
    private DataTable GetNewTaxesTable()
    {
        // Creates a new table
        DataTable table = new DataTable();

        // Adds the required columns for tax classes
        table.Columns.Add("SKUID", typeof(int));
        table.Columns.Add("TaxClassDisplayName", typeof(string));
        table.Columns.Add("TaxValue", typeof(double));

        // You can also add other (optional) columns:
        //table.Columns.Add("TaxIsGlobal", typeof(bool));
        //table.Columns.Add("TaxClassZeroIfIDSupplied", typeof(bool));

        // Returns the created empty table with predefined columns
        return table;
    }

    /// <summary>
    /// Creates a row in a tax table.
    /// </summary>
    /// <param name="taxTable">Tax table to which the row is added.</param>
    /// <param name="skuId">ID of the taxed product.</param>
    /// <param name="taxName">Display name of the added tax.</param>
    /// <param name="taxValue">Percentage value of the tax.</param>
    /// <param name="taxIsGlobal">True if the tax is global. False (default) if the tax is site-specific.</param>
    /// <param name="zeroTaxIfIDSupplied">True if the tax is 0% if the customer is a company
    /// with a tax registration ID. False (default) if the tax is for all customers.</param>
    private void AddTaxRow(DataTable taxTable, int skuId, string taxName, double taxValue, bool taxIsGlobal = false, bool zeroTaxIfIDSupplied = false)
    {
        // Creates a new row
        DataRow row = taxTable.NewRow();

        // Sets the required columns of a tax class
        row["SKUID"] = skuId;
        row["TaxClassDisplayName"] = taxName;
        row["TaxValue"] = taxValue;

        // You can also set other (optional) columns:
        //row["TaxIsGlobal"] = taxIsGlobal;
        //row["TaxClassZeroIfIDSupplied"] = zeroTaxIfIDSupplied;

        // Adds the row to the tax table
        taxTable.Rows.Add(row);
    }
}