The order of the calculation

Customs value is the goods plus freight and insurance. Duty is a percentage of that value. Import VAT or GST is then charged on the customs value plus the duty plus any other amounts the authority includes, so tax is paid on the duty too. Brokerage is added on top.

With the default figures: 200 + 30 + 10 = 240 customs value; 10% duty = 24; 20% tax on 240 + 24 + 5 = 53.80; plus 12 brokerage gives 89.80 in charges. Read how import duty and VAT are calculated.

What a percentage cannot cover

Some goods carry specific per-unit duties, quotas, anti-dumping duties or excise. Duty rates can depend on where the product was made, not where you bought it; see country of origin vs place of purchase. Low-value thresholds change, so do not assume one applies. Confirm with the destination customs authority or a broker.