OSRS GE Tax Calculator

The Grand Exchange takes a tax from the seller when a sale completes.

Tax = min(5,000,000, max(1, floor(sale price × 0.02))). You receive the sale price minus that tax. The buyer pays no tax.

Sales above 250,000,000 gp all pay the 5,000,000 gp cap, so the effective rate falls on the most expensive items.