Germany, Austria and Switzerland
You can leave the church by appearing at a government office with the required documents in both Germany and Austria, but in Switzerland you are forced to go to the parish office. Germany collects “church tax” through your income tax and you should retain proof that you have left the German church, or you could still have to pay.
In 2009 the tax deductability of the church tax cost the German state € 2.94 billion in lost tax income.  And the next year “church tax” brought the German churches €4.794 billion.  The only way to end this is to formally leave the church.
Over the years consistently more Lutherans have left the German churches than Catholics.  However, in 2010, amid continual revelations of child abuse by priests, so many Catholics died or left that the Catholic Church in Germany shrank. 
Austrian “church contribution” (Kirchenbeitrag). In Austria the churches collect their own taxes which they base on personal income. To avoid this obligation it is necessary to leave the church.
The resignation in April 2010 of an archabbot after admitting to sexually abusing a young boy caused a steep rise in church-leaving, in fact, more in the first half of 2010 than in the whole of 2009. The archabbot had offered the now adult victim €5000 to keep quiet ― leading some Austrians to suspect that their “church contribution” didn't always go to charity. Swiss “church tax” (Kirchensteuer). In Switzerland church tax is levied by each canton for the religious groups it recognises. And it's not just people who have to pay. In 18 of the 26 cantons firms must also subsidise the churches, even though they've never been baptised and they can't leave the church. This is now being challenged by a computer specialist who belongs to no church himself, but must still pay church tax for his one-man company. In September 2010 the Swiss Supreme Court ruled that this was constitutional and now he is taking his complaint before the European Court of Human Rights. 
Leaving the church in Germany
Warning #1: Don't lose your church-leaving certificate!
Request a church-leaving certificate, as it is not automatically issued. You must be able to prove that you have left the church legally — your word is not enough. Some religious groups speculate that former members may not keep their certificates of church leaving, and, years later, demand proof of this. If you can't produce your certificate of leaving the church, you are liable for church tax for the previous six years. And this applies to foreigners, too — if you've been baptised, you have to officially leave the church to be freed of the legal obligation to pay chuch tax.  Especially in German states such as Berlin where the churches are losing many members, religious groups use this method to get money.
Warning #2: Be aware of the consequences
If you apply to leave a German church you may receive a form letter warning you that you'll be denied a Christian burial , but in practice a plot in the churchyard should be no problem and there are many community graveyards.  However, unless you rejoin the church for the occasion, you cannot have a church wedding, be a marriage witness or a godparent.  You will also have little chance of enrolling your children in Catholic schools or kindergartens.  Furthermore, you can expect to be fired from any of the church-run institutions, Catholic or Protestant which, after the state, are the Germany's second largest employer.  Not only economic, but also social pressure may be brought to bear: the priest may even announce in church, before to all your friends and family, that you have left. 
In Germany you must declare your intention to leave the church at a government office. For details (in German) click on your state in Germany on the drop-down menu on the left at http://www.kirchenaustritt.de/english.htm
Where do I make the declaration? What does it cost?
You must appear in person at the registry office (Standesamt) of your municipality/district (Gemeinde) or at the local court (Amtsgericht) — depending upon where you live (which Bundesland) in Germany.
There you fill out a form and sign it. You need a valid identity card (Ausweis) or passport (Reisepass). If you are married or divorced you may also need your family book (Familienbuch). You need not say why you wish to leave the church.
You cannot leave the church by writing a letter!
Alternatively, you can leave the church by making a declaration before a notary (Notar). However, for this you will have to pay notary fees (Notargebuehren).
The fee, (where it exists), varies according to your state in Germany. [Up to €50]
How old must you be to make a declaration that you want to leave the church?
Under 12 years of age:
A child cannot make his own declaration in order to leave the church. His parent or legal guardian must act on his behalf.
Between 12 and 14 years:
A child of this age still cannot make his own declaration. Here, too, his parent or legal guardian must act on his behalf. However at this age it now requires the expressed permission of the child.
From 14 years:
Now the young person can finally make a legally effective declaration to leave the church on his own. The permission of the parents is not necessary.
In Germany church tax has a long history. In the Middle Ages Princes of the Church extracted the “tithe” from the peasants (a tax of one tenth of their income). Because of the close relationship between church and state in Germany, the government tax office collects this money to this day.
You can tell from your wage tax card (Lohnsteuerkarte) whether or not you must pay church tax:
On the right side under “Church tax debit” (Kirchensteuerabzug) there will be two lines. If there are initials on these, (for example, "EV" or "RK"), that means you are a church member and pay church tax.
Leaving the church in Austria
You must declare that you are leaving the church to the local authority (Bezirkshauptmannschaft), for example to a magistrate (Magistrat) in a city (Statuarstadt).
You need an photo identification (Lichtbildausweis) and a receipt from the office where you register where you live (Einwohnermeldeamt) and perhaps also a change-of-name document (for example, a marriage certificate).
From the age of 14 you can leave the church even without permission from parents or guardians.
As with all other administrative procedures, it's also sufficient to apply in writing by registered letter (eingeschriebener Brief).
You will find the address of your local authority at http://www.kirchenaustritt.at/
Leaving the church in Switzerland
To leave the church you must make a declaration in writing at the parish office.
Your letter should contain your declaration (Austrittserklärung) as well as your personal details.
You need not give any reason.
“Wie trete ich aus der Kirche aus?” http://www.spart-euch-die-kirche.de/kirchesparenwie/wietreteichausderkircheaus.html
This reassuring site says that “Jesus of Nazareth didn't want a church that was interwoven with the statte and certainly not a church tax”. At the end it offers free advice with no obligation from a former pastor and a former priest.
“Leaving the church in Germany”, kirchenaustritt.de. http://www.kirchenaustritt.de/english.htm
1. Wasmuth v. Germany (12884/03) ECHR Chamber judgment 17.02.2011. http://www.echr.coe.int/NR/rdonlyres/80119CA2-3425-43D9-9FEB-524829C637B1/0/FICHES_Libert%C3%A9_religion_EN.pdf
2. Die Absetzbarkeit der Kirchensteuer als Sonderausgabe verursachte im Jahr 2009 Steuermindereinnahmen von 2,94 Mrd. Euro. Source: 22. Subventionsbericht der Bundesregierung, S. 79. http://www.ibka.org/presse10/sparpaket-kirchensubventionen
3. “Victims’ groups dismiss abuse compensation plan as a mockery”, The Tablet, 11 March 2011. (Of the €4.794 billion in “church tax”, collected by the state in 2010 the Catholic Church receives more than half.)
4. Kirchenaustritte in Deutschland (1992-2008). http://www.kirchenaustritt.de/statistik/
Over the long term, the exodus from the churches hit a peak shortly after the unification of Germany in 1989, presumably because those in the in the former East Germany, (predominantly Lutheran), found that they were henceforth going to have to pay “church tax”. However, after declining from that historic high point, the numbers had been steadily rising again, even before this latest peak.
5. “More German Catholics quit Church over sex abuse”, Reuters, 7 April 2011. http://www.msnbc.msn.com/id/42473454/ns/world_news-europe/t/more-german-catholics-quit-church-over-sex-abuse/
6. A reader comment to the 3 March 2010 report that the Arch-abbott had resigned after trying to bribe the victim into silence the year before was that “...you're paying [for this] with your church contribution!” http://www.gegensexuellegewalt.at/2010/03/09/erzabt-von-stpeter/
7. “Gang nach Strassburg von Schwyzer Informatiker”, Schweizer Radio und Fernsehen, 6 April 2011. http://www.drs.ch/www/de/drs/nachrichten/regional/zentralschweiz/257633.gang-nach-strassburg-von-schwyzer-informatiker.html
8. Grenzenlose Kirchensteuer-Abzocke in Berlin, IBKA, 17 February 2015. http://www.ibka.org/kirchensteuer-abzocke-berlin
9. “Marcus, 44 Jahre”, Austrittsberichte, http://www.kirchenaustrittsjahr.de/node/11
10. “14. Wie sieht es mit dem Begräbnis aus, wenn ich ausgetreten bin?”, IBKA. http://www.ibka.org/infos/kirchenaustritt-begraebnis
11. “Ausstieg leicht gemacht”, TAZ, 6 February 2009. http://www.taz.de/1/leben/alltag/artikel/1/ausstieg-leicht-gemacht/
12. Nettolohn.de Lexikon: “Kirchenaustritt”. http://www.nettolohn.de/lexikon/kirchenaustritt-118.html
13. “How far can German churches discriminate against 2.5 million employees?”, Concordat Watch.
14. “Welche Folgen kann ein Kirchenaustritt haben?”, Kirchenaustritt: Ratgeber, Infos, Tipps. http://www.praxis-lexikon.de/diy/diy-bauplan/k/kirchenaustritt.php