"When the people forget their duty they are no longer human and become something less than beasts. They have no place in the bosom of Humanity, nor in the heart of the Emperor. Let them die and be forgotten."
The Tithe Grade is a bureaucratic designation of the Adeptus Terra that determines the amount of raw materials, resources or soldiers an Imperial world must supply to the Administratum as taxes or tithes to keep the Imperium of Man's interstellar government functioning. It also includes each world's need to fill the ranks of the Astra Militarum or provide human psykers to the Black Ships of the Adeptus Astra Telepathica.
The size and nature of the Imperial Tithe depends on the type of world it is applied to, as a large Hive World like Necromunda will be expected to provide a much larger tithe than a pre-industrial Feudal World. A tithe can be any type of resource native to the world: food, weapons, minerals, manufactured goods, soldiers, psykers, etc.
Space Marine Chapter Homeworlds and Forge Worlds do not normally provide tithes to the Imperium since their resources are to be used to maintain the Space Marine Chapter that controls them or to provide manufactured military goods and vehicles to the Imperium, respectively, so both are given the tithe grade Aptus Non. Agri-world tithes generally refer to what percentage of the planet's food production must be supplied to the Imperium.
Also called "Terra's Due" or the "Grand Harvest," the Imperial Tithe is a complicated contract worked out according to each planet's ability to pay. A great many branches of the Adeptus Administratum are involved in the process, and different organisations might be tasked with sacred duties such as assessing tithe rates, measuring collections, and monitoring any fluctuations.
It is the duty of each Planetary Governor to ensure the Imperial Tithe is paid. Such ministrations are tyrannically enforced, but as long as all tithe responsibilities are met and enemies of the Imperium are rejected, a Planetary Governor may rule his planet in any fashion he sees fit with little or no interference from Terra. In return for this fealty, the Planetary Governor can call upon the Adeptus Terra in times of need to request aid.
Over the long centuries, many planets have established their own unique customs and traditions for how they supply their tithes. For instance, Vostroya, a manufacturing planet, supplies every firstborn son to service in the Imperial Guard, while the four planets of the Nepstrum System take volunteers from the established family-holds for the Imperial Navy and press-gang the remaining numbers from the worker class.
Failure to deliver the Imperial Tithe is met harshly. Even the slightest breach in protocol will often result in the execution of the Planetary Governor and a swift and thorough regime change. Despite the number of Adepta tracking planetary tithes, sometimes it takes time for discrepancies to surface and be acted upon. This is inevitable given the difficulties of interstellar space travel and communications, to say nothing of the vast bureaucracy within each of the many organisations that make up the Adeptus Administratum.
Once tithe anomalies are spotted, however, the Imperium moves with brutal finality. None can say how many worlds' rulers are unfairly replaced due to minor accounting errors, but the Imperium is at war, battling not for planets or even star systems, but for the survival of the human race itself. The selfishness of the few will not be tolerated in the drive to stave off the extermination of Mankind.
The Emperor's Gift
Every planet in the Imperium owes loyalty and gives tithe to the Emperor. Whether this is collected once every solar cycle or once every one hundred standard years, it is the first and most important responsibility that the Emperor demands of His subjects. Because of the importance of a planet's tithe, it has on many worlds become a sacred day known as the Emperor's Gift. On this day when millions of tonnes of ore, precious metals or foodstuff are borne skyward, citizens look up and give thanks to their contribution to the great work that is the Imperium. It is also on this day that a world offers up newly-raised Imperial Guard regiments, fresh-faced soldiers who leave their world forever to serve the Emperor among the stars.
These men and women spend the day of the Gift enjoying themselves and are refused very little by those they leave behind. In some places across the galaxy, it is considered good luck to serve such soldiers before they depart. The Gift is also a time of fierce pride amongst citizens towards their world, making it dangerous to be an off-worlder, for slandering the name of the planet during the time of the Gift is almost guaranteed to start a fight. Some have speculated that it was, in fact, not the Ecclesiarchy but the Administratum that sanctioned this holiday. After all, how else could you hope to strip a planet of its wealth and leave it feeling so good?
Raising the Tithe
Every world within the Imperium is ruled over by a Planetary Governor or Imperial Commander. Whether such men and women inherit their title by blood or are awarded it for some great service in the Emperor's name, their responsibilities are the same. These Governors are afforded absolute authority to rule their realm precisely as they see fit. In return, however, each Governor is beholden to the wider Imperium, expected to ensure that a set of key responsibilities are fulfilled without fail. Each Governor is responsible for the day-to-day defence of his or her own realm, for the Astra Militarum cannot be deployed to handle every brush-fire war, piratical raid and minor incursion. To combat such threats, Governors are expected to raise, train and equip their own Planetary Defence Forces to safeguard their holdings. Fortifications must be raised, manned and maintained, the skies must be watched, and the populace must be carefully monitored lest the outer dark creep into the hearts and minds of loyal Imperial citizens.
Perhaps most importantly, there is the Imperial Tithe. Based upon archaic criteria assessed by Departmento Munitorum officials, each world must provide one tenth of its total military force to fight for the Imperial Guard. It is an offence punishable by death for a Governor to supply substandard soldiery when the tithe is exacted, or to provide insufficient numbers. Furthermore, it is a capital offence should these soldiers lack proper uniforms, sufficient training, or appropriate levels of genetic purity. For these reasons, though some worlds recruit by caste, population density, geography or even lottery, most Governors are given to pouring their best men into such regimental foundings. This is less out of a sense of altruism or duty than it is an ongoing effort of self-preservation. Nonetheless, on many worlds it is a matter of some honour to be chosen for this duty. Indeed, it is not uncommon for lives to be lost in the fierce competitions that the tithe often spurs. In a few rare cases, such as the Bardellan Wars of Proving or the Charon's Cluster Schism, localised wars can even be triggered in the lead-up to the month of tithing. Planetary authorities are normally quick to crush such counter-productive disputes, fearful of the concurrent waste of tithe-grade manpower and the apparent loss of political control in front of Munitorum officials.
In times of great peril, the Departmento Munitorum is permitted to call upon Governors to raise quantities of forces substantially above their normal tithe. Such measures can see entire cities or continents all but emptied, or key societal strata removed en masse. When the Imperium demands its pound of flesh it is not within a Governor's rights to refuse, and each knows that next time it could so easily be his world that requires the protection of the wider Imperium. Only through compliance with the tithe can such security be guaranteed, for only worlds of proven loyalty may rely upon receiving Imperial aid when their own defences prove insufficient. Isolated worlds will not long survive, and the Munitorum's most economical recourse to punish rebellion is often simply to cut a world loose from the Emperor's protection.
Known Tithe Grades
The make-up of a given world's tithe payments, regardless of the size of those payments as indicated by the Tithe Grade, is determined by the section of the Administratum responsible for the overall governance of that world's sector and sub-sector of space. The known Imperial Administratum Tithe Grades are listed as follows, from highest (most tithe required) to lowest (least tithe required):
- Exactis Extremis - The largest Tithe Grade
- Exactis Particular
- Exactis Median
- Exactis Prima
- Exactis Secundus
- Exactis Tertius
- Decuma Extremis
- Decuma Particular
- Decuma Prima
- Decuma Secundus
- Decuma Tertius
- Solutio Extremis
- Solutio Particular
- Solutio Prima
- Solutio Secundus
- Solutio Tertius
- Adeptus Non or Aptus Non - No tithe required due to past events like an Exterminatus rendering the world lifeless and unproductive or if the world already provides an important service to the Imperium, such as a Space Marine Chapter Homeworld or Adeptus Mechanicus Forge World.
- Codex: Astra Militarum (6th Edition), pg. 14
- Warhammer 40,000: Rulebook (6th Edition), pg. 148
- Warhammer 40,000: Rulebook (3rd Edition), pp. 114–115