Tithe

They paid ten shillings a gig; of this I gave Mother nine, who in turn gave seven to the church for the Poor of the Parish. I couldn't understand it, we were the Poor of the Parish. A tithe (from the Old English word meaning a "tenth") is a contribution given to support a religious organization or charitable efforts consistent with the teachings of a religion. Tithing may be compulsory, enforced and administered by the state or the religious organizations themselves, or may take the form of voluntary donations. Tithing should not be confused with sporadic donations, since a tithe is a formally mandated act of charity — based on providing a percentage of income in support of the religion or its goals. In pre-industrial societies, a tithe tends to take the form of a percentage of agricultural produce, while in modern societies God prefers cash, lots of cash. Believers may pay a tenth of their income before tax or after tax.

Collection methods
Tithing is by no means consistent across all of the religions and denominations. Some religious groups do not practice tithing — preferring to solicit donations to the church or causes consistent with the practices of the religion. Some religions benefit from state-administered taxes; some receive the tithe directly from their congregations; others trust members to give their money directly to the needy; and finally, there's the good old-fashioned collection plate. Strictly speaking, the approach of soliciting sporadic donations is not necessarily considered to be tithing.

Some states levy what is commonly known as a "church tax". Under this system, the state would collect the funds and then distribute them to a state religion or a selection of religious organizations, depending on the country in question. An example of a state-administered tithe can be found in Sweden, in which members of the Church of Sweden pay a tax to support their religion. Such taxes may be compulsory or based on religious affiliation or willingness to pay. The proceeds may be in support of a specific religion, or such as in the case of Switzerland, distributed among a selection of religious organizations.

Some religious organizations require (or at least compel) members to tithe directly to the organization in question, which then administers the funds as it sees fit. An example of this is found in Mormonism. In other cases, members are expected to offer charity to causes consistent with the beliefs and goals of the religion in question, and the tithe is not administered by the religious organization. The latter approach is practiced in Judaism.

Variations among major religions
Tithing is common to most major religions, although the way in which tithes are collected and administered is subject to variation among religions and denominations.

Christianity
In Christianity, tithes are typically collected and administered by churches. In some countries, the state imposes a church tax in support of one or more chosen religious organizations.

In the absence of a church tax, Christian churches tend to compel their members to donate to support the activities of their church, either by tithing or through the offering of alms. In Catholicism, this is most visibly seen in the form of the collection plate that gets passed around, sometimes multiple times, during religious services. Although not compulsory, it's arguable that there's significant peer pressure to offer substantial donations, rather than just low-value coins and bottle caps.

Some churches still practice strict tithing, such as the Church of Jesus Christ of Latter-day Saints, otherwise known as Mormonism, and the Philippines-based Iglesia ni Cristo. Members of the church are expected to contribute one tenth of their annual income to the church.

Judaism
Judaism has a tithe in the form of tzedakah — a Hebrew word for charity. It is a religious obligation to donate at least 10% of one's income for charitable purposes, and such donations would not be made to the temple or synagogue; instead, they are typically given directly to charities or people in need. The origin of this practice is found in Deuteronomy 14:22. Most synagogues rely on membership dues for their operating expenses.

In addition to monetary tithes, Leviticus 27:30-33 required the Hebrews to give one out of every ten units of their crops and livestock to the temple; and in the case of livestock, there was no redeeming a prized animal if a priest selected it for tithing.

Islam
Islam has Zakat, a 10% form of social security and system of wealth distribution which redirects money towards the poor and towards the upkeep of religious institutions. The system is so complex, however, that you really need a university degree to do it properly.