In their own Assault phase, a player can declare a charge with any of their units that are within Assault range of an enemy unit and not already in close combat. Assault range is typically 6" but some units can assault 9", 12" or more. Where this is the case, it will be noted in the unit's special rules. The unit may charge any enemy unit that can be contacted by at least one of its models making an Assault move which avoids any obstructions such as impassable terrain or other enemy units which you do not wish to contact.
A unit that fired in the Shooting phase of the current turn may only declare a charge against the unit it shot at. A unit that remained stationary in the Movement phase in order to fire heavy weapons or fire twice with pistols or rapid-fire weapons may not charge at all in the Assault phase.
A unit may charge multiple enemy units but only if the charging unit can reach them all without losing unit coherency. Select one unit as the primary target and move to engage that one first as detailed below.
If the unit fired in the Shooting phase it must start its charge by engaging the unit it shot at first.
Exception: Models such as Terminators, Bikes, Dreadnoughts and Walkers, which always count as stationary when firing, do not have to charge the same unit they shot at.
Designer's note: The change to having to charge the target of your shooting is an important one - the old assault unit tricks of hitting one unit with ranged attacks and then charging a different enemy can no longer be used (unless you can reach both, of course). This helps bring assault units more into line with firepower-based ones in that they can only attack one enemy unit in their turn. The one exception to this is units such as Hormagaunts which are both very fast and very numerous, as these may be able to engage several enemy units at once, effectively swamping the enemy defence. Also note that a unit doesn't have to charge the nearest enemy unit, although it can be difficult to bypass one unit to reach another, as we'll see later.