2.15  INCOME  The normal income (in BPs) from each area you control is equal to the population in that area. Income is actually added to your balance at the end of the previous turn, and maintenance deducted, so that the balance shown in your player report is the number of build points available for the coming turn. Your game report shows separate totals for "income" (which is what you earned), "BPs" (which is what you've got available to spend, after maintaining your armies etc) and "treasury" (see 2.8). A table of income examples is included in the quick reference section.
VIKINGS: Viking kingdoms receive extra BPs in income each turn (representing the income from their homelands) equal to the turn number. The extra does not apply to a new Viking kingdom the turn it is formed.
TRADE: Income from trade levels is paid into your treasury (rather than current balance) each turn, and for each city is equal to whichever is less of the population and trade level (but see blockades, paragraph 2.16). The same is paid into the treasury of the owner of the hinterland of the city (even if it's owned by a different player).

2.16  BLOCKADE  A city is considered to be blockaded if the surrounding area (the hinterland) is owned by a different player to the owner of the city and contains a number of armies greater than half the total population and armies inside the city. A blockaded city produces no income and may not make BUILD, FORTIFY, GROW, LEVY, MIGRATE, RAZE or RESERVE actions. Blockades are automatic, and occur whenever you control an area with a city in it that you don't own (provided you have enough troops).
Note: A blockade is a reasonable alternative to conducting a siege against a well defended city. The owner of the city must either negotiate for the blockade to be lifted, or defeat the army. But if the city is rich you may want to avoid blockading it so as to earn your share of income from trade.
Note: The cities in Ireland may be blockaded in the normal way although if you do not control the adjacent sea area then the blockade is unlikely to last very long (the owner will simply ship troops in from outside).

2.17  ORDER OF PLAY  The order of play in "Dark Age" is an extremely important feature of the game, which has many implications for the way the game is played. The game is adjudicated in sequence, one action at a time in strict order. One action is processed for each player in turn, in the order given on the turnsheet (ie. the first action is processed for each player, then the second action for each player, and so on).
The order in which each round of actions is processed is fixed for the turn, but players may spend build points to change the order for the following turn (see 9.1). The order of play for a given turn may be extremely important. The initial order of play (for the first turn) is random.

2.18  UNOWNED AREAS  At the start of each turn, before any player actions are  processed, one random action is processed for each area which is unowned (except cities under blockade). These actions are not subject to the normal rules, and may increase the fortification or population level, or levy an army. Army levies are possible (but less likely) in areas with insufficient income to pay for them. Population can appear in unpopulated areas (for this reason you may wish to abandon such areas until the population returns).