You can set the default purchase related values such as the default currency, tax rate, billing & shipping address, and terms of purchase here.

Enter the default currency (For example, USD or $). This will be displayed in all the purchase orders (PO) generated and in any place where money is being used.

The default tax rate that you enter in this field will be the tax rate used for calculating the sales tax in all the POs generated. If you want a different tax rate for any specific PO, then in the PO creation, enter the rate that you want for that PO.

If you want to tax shipping also, by default, then select the check box beside Tax Shipping field.

Enter the shipping address to which the PO items will be shipped and the billing address to which the invoice and bill needs to be sent.

Enter the PO terms in the Terms text box. Click Save to save the settings.