A duty refers to the bonus items awarded when a socketable item named "Toll ware X" (where X is the bonus item designated) is set and activated in any warehouse. The item itself will also specify two key values: the numerical amount of any goods set as the sale limit, and the amount of bonus goods added to that warehouse when that sale limit amount is exceeded.
These items can't be researched at the Academy: you have to find or buy them.
These three scenarios explain clearly how the duty items work.
1. A warehouse contains a 5 ton duty of 3D Projectors on any amount above 18 tons.
2. Any NPC's trade ship visits the warehouse and buys 20 tons of Sand and 30 tons of Tools.
3. Because one or more goods purchased exceeded the 18 ton limit, 5 tons of 3D Projectors are added to that warehouse immediately when the sale takes place.
1. A warehouse contains a 5 ton duty of Pasta Dishes on any amount above 20 tons.
2. The same warehouse also contains a 5 ton duty of Communicators on any amount sold above 18 tons.
3. Any NPC's trade ship visits the warehouse and buys 19 tons of Fish, 8 tons of Concrete, 12 tons of Steel, and 2 tons of Luxury Meals.
4. Because a sale was made (Fish) that exceeded a duty limit, 5 tons of Communicators are added to the warehouse.
5. But because no sale of any goods exceeded 20 tons, no Pasta Dishes are added.
1. A warehouse contains a 5 ton duty of Plastics on any sale above 20 tons.
2. Any NPC's trade ship visits the warehouse and buys 180 tons of Heavy Weapons, 200 tons of Steel, and 200 tons of Bio Drinks.
3. Because a sale was made that exceeded the 20 ton limit, 5 tons of Plastics are added to the warehouse immediately when the sale takes place.
- Duty items can only be socketed and activated. Once activated, they cannot be removed from their warehouse socket without being "destroyed".
- Duties only apply to sales made by NPC trade ships, they have no effect when a player-controlled ship makes a sale.
- Duty items are relatively rare, yet usually fairly inexpensive, costing about 140 or so licenses. A 5 ton duty on 3D Projectors received from selling over 20 tons of Building Modules/Sand/any normally cheap goods can then be sold to Yana Rodriguez for 483 x 5 = 2415 credits. A duty of 5 Pasta Dishes can be sold to Yana for 183 x 5 = 915 credits.
- NPC trade ships visit every island including unpopulated ones containing only industry. While power production and maintenance reduction bonus items may be preferred for populated islands' warehouse sockets, it would be worthwhile to build an additional sand extractor (most NPCs buy sand) on an island that can spare an additional socket if a valuable duty is found/bought. A "sell" command for the duty item to a nearby ark/warehouse can then be added to the supply route instructions of a ship which visits that island.
- Take care that the duty is an item that's needed. For example, a duty of 5t Building Modules is unlikely to be a good use of licenses, especially in a multiplayer game.
- Due to the unpredictable nature of NPC trading, it is inadvisable to depend entirely upon duties to supply any of the needs of a population.
- Duties are more likely to appear in the selling inventories of NPCs once the highest level of relations is reached.
- Certain higher-level duty goods for which NPCs will pay a premium price can prove decisive in longer games. The cumulative sale of such "free" goods from even a single well-utilized duty can quickly add additional ships to a fleet. Even if the extra credits can only provde a simple Freight Ship, this "free" ship can nevertheless be significant if equipped with a Detonator or Pulse Bomb.
- High-end 'needs' items (Pharma, Biosuits) can be supplied exclusively though duties. You can have multiple duties on an island or simply have one on a heavy trade island. Alternately, set up a smart trade-route for each NPC ark. Buy their cheap faction-exclusive building materials (ie. Wood from Yana) and set up fire-sale (all the stock, low prices) trades on your receiving island (the one with the duty). The respective faction representatives will constantly be purchasing enough wares to fulfill the duty requirements, and your population will remain content. / / only works with highest-end wares, others are used much too quickly for trades to maintain them / /