Restrisiko wrote:

Ground units regenerate everywhere in your own territory. This of course includes all provinces you have conquered.
No cure on hostile, neutral or allied area.

Airplanes regenerate on own airfields or if in the air from there, even if they are on an attack flight or on patrol, also over enemy territory, but they have to start from your own airfield (be based on it).
No cure on carriers or allied airfields or when in the air from there.

Warships regenerate everywhere - wherever it's enough water under the keel..
Ground or air units don't regenerate at sea or disembarkation, only during embarkation from own territory.

All units regenerate also during movement or in combat, even in closed combat - provided the other requirements are fulfilled. Whereas healing with gold is not possible in close combat.

The regeneration takes place automatically at the day change.
How much depends on the damage respectively the remain condition.
The less the condition is, the greater is the cure.
The formula for regeneration is: Damage x 0.15

Decimal places in the repair height are randomly rounded up or down.
That's why sometimes no healing occurs when the existing condition is 94% or higher - you need fortune then.
The morale of the provinces or to place an unit in a fortifications has no influence for healing.

Examples:
At 1% condition >> damage 99 x 0.15 = 14.85 healing sum, randomly rounded = 15 or 14.
At 10% condition >> damage 90 x 0.15 = 13.5 healing sum, randomly rounded = 14 or 13.
At 50% condition >> damage 50 x 0.15 = 7.5 healing sum, randomly rounded = 8 or 7.
At 90% condition >> damage 10 x 0.15 = 1.5 healing sum, randomly rounded = 2 or 1.
At 94% condition >> damage 6 x 0.15 = 0.9 healing sum, randomly rounded = 1 or 0.
As at 94% to 99% condition, healing is always either 1 or 0.