Ok....... so here how it works....
You contact your catholic diocese office and tell them you want to start an anullment. They ask you a bunch of questions and send you some information. You must be actually legally divorced before you start this process.
They send you a packet of information that is about 5 - 6 pages of short answer questions. By the time I got done writing all my answers - my response was about 20 pages long. The whole point of an anullment is to find out if there was something "wrong" with the couple at the time they were married that would have prohibited that marriage from being a valid marriage according to cannon law.
So.... some of those things are... if you intended to contracept. Since cannon law requires you to be open to life - intending upon your marriage to use contraception would make your marriage invalid because according to the church unless you intended to do anything other than NFP - you shouldn't have been getting married in the first place. So, something was impeding you from giving valid consent. Other examples are things like if when you got married you didn't necessarily intend for it to last until death do you part. So, if you knew there were issues and still got married and figured well if it doesn't work - we can just divorce, that would NOT be valid consent because you were supposed to be intending on till death do you part. If one of you were being coerced - like there was a pregnancy and you felt like you HAD to get married - that could make the marriage in valid. In some cases not having enough pre-marriage counseling or classes so that you can claim you didn't understand the permanence of marriage may be a ground for annulment.
It is not "catholic divorce" and it doesn't make any kids illigitimate. It simply means that at the time of consent you did not or were not able to give complete consent.
So, you do your questionaire, then they assign you an advocate, or will essentially argue in person your "case" before the Tribunal - who are a bunch of cannon experts. Your advocate reviews your questionaire with you, determines what grounds he will ask for and writes some stuff. Meanwhile at least 3 "witnesses' will also get questionaires from the Diocese - they have to essentially fill out questions about you at the time of your marriage and their responses will hopefully back up the grounds that your advocate works out. Then your EX will also get a similiar form.
Then once they get everyone's info back ( they give you 30 days as the ex to respond then they just deem you non responsive) they move the annulment on and it is taken to the tribunal. Your advocate either in person or in writing argues for you, and someone else is appointed to defend the marriage.
Then the tribunal rules if there were sufficient grounds to declare your marriage null. Then if they do, it is given to the appeals board who reviews it, and if they agree - then you receive your annulment.
It is possible with cases where someone is married many times or there seems to be some other psychological issues, that the Tribunal will require that that person have additional counseling or pre-cana or that they have to have a waiting period etc.
The Church will not schedule your wedding until you have received your Declaration of Nullity.
Since, the Church automatically considers any subsequent marriages invalid by the sheer fact that they weren't eligible to be married for second or third or fourth time until they had their prior marriages anulled, annulling the subsequent marriages is considered procedural and while you have to fill out paperwork, etc you will receive the Declaration of Nullity for subsequent marriages without the whole dog and pony show listed above. So, you go through the big process the first time, and the other ones are just paperwork.
There are slight variations from Diocese to Diocese. They cost the same no matter who you are - around $500 bucks, BUT they will still do it if you say you can not pay.
Relatively speaking it is fairly easy to nullify a non-catholic's prior marriage. For one, they probably intended to contracept. They also generally aren't required to do any pre-marriage counseling or classes - so they can claim they weren't prepared and didn't get that marriage was for life - easier than a Catholic can. Because for Catholics, they are supposed to go to the pre-cana, etc, and where they have the permanence of marriage drilled into them - so its hard to claim that.
My anullment as a non-catholic to marry my Catholic DH took about 9 months. They average 18 months. But, I am super organized and anal and got my friends to get their stuff back right away and sort of kept on the process. The time was a bear. I probably spent 60 hours on my questionaire and research to make sure I understood what "grounds" were and following up on things.
ETA - if you are a Catholic who marries outside of the Church - like a justice of the peace wedding - your marriage is considered invalid - and that is a MUCH simpler quick process.
connie