This might seem like a silly question, but I am not a Catholic, and so I do not know the answer!
Do Catholics tithe?
Catholics don't tithe.
From the Catechism of the Catholic Church:
Of course, this doesn't mean they don't give. And Catholics are obligated to give, according to ability. This isn't just semantics, there's a difference between the two.
A tithe in this context isn't just an offering, it's a specific percentage of a person's salary that the person must give to their church, usually under pain of sin. This was required by the Old Law, but is no longer required. Charity (a special formal word that means love) obliges us to give, though. How the offering is gathered might depend on the particular parish, but it's roughly what you'd expect.
Sometimes, some of us even sing a song about this issue. Some of the lyrics go:
By "feast" we mean the Most Holy Eucharist, the Most Sacred Blood, God literally present before us, just as He was Himself present before St Thomas the doubter.
We sing that song being mindful of Isaiah 55:
However, again from the Catechism:
On the obligation to give, 2 Corinthians 9:
Addressing the Old Law, Romans 13:
A person who has love for her Church will give an appropriate offering. In the same way that St John took care of Holy Mary, Mother of God, so too do we presently seek to take care of the Christ's Bride until she is reunited with Him at the end of time. In turn, she takes care of those who are in need (the Catholic Church is, among other things, a really, really big decentralized charity).
Well, I've been to Catholic services, and I have witnessed a basket being passed around wherein money is placed. If tithe is defined as putting money in that basket, then yes, they do.
Officially, that is, according to Roman Catholic doctrine, the Catechism, §2043, states
Thus, the idea is that you are not commanded to give a certain percentage, although "tithe" literally refers to 10%. Rather, it is expected that one give according to his ability.
Catholics in Germany pay 8%-9% of their income tax to the catholic church. It's deducted directly from the paycheck like a tax and it's actually called Church Tax (Kirchensteuer). That seems to qualify as tithing. Now the church may claim that this is an artifact of German law and not their doing. However, they sure as heck take the money and I've certainly never see them refuse it because it wasn't given voluntarily. [EDIT: the tax is based on income tax and not taxable income, total revenue in 2012 was 5.8 billion Euro which is about 8 billion dollars]