Perform calculation if checkbox checked

Hi there. I’m brand new to Airtable and loving it so far. I’m trying to figure out how to perform a calculation based on a checkbox field. My table is for my business accounting. I have an “Amount” field and a “Taxable?” Checkbox. If I have the checkbox checked I would like to multiply the amount field by my provincial tax rate to calculate the amount of tax on the purchase. It doesn’t seem to accept a formula for the logical true result. Is this possible? Thanks.