This is a very condensed, easy to understand explanation of the I-601 process.
WAIVERS ARE NOW FILED IN THE US AT A LOCKBOX – ALSO THOSE WITH ONLY UNLAWFUL PRESENCE AS AN INADMISSIBILITY ARE ALLOWED TO FILE I-601s WITHIN THE U.S. AND WAIT TO HAVE THEM ADJUDICATED BEFORE GOING TO THE CONSULATE TO GET THEIR VISA.
First, an I-130 or I-129F is filed with required documents and a fee. These may have to be filed at a CIS (Citizenship and Immigration Services) lockbox (special P.O. box). Approval normally takes two to five months.
Second, the I-130 or I-129F is approved and the case is forwarded to the NVC (National Visa Center) for I-130s or the consulate for I-129Fs. More forms and required documents are filed (for an I-130 they are DS-230 – or DS-260 online – and I-864 Affidavit/s of Support; for I-129F the required forms vary widely) and more fees to pay. How many forms depends on where you file and if you need more Affidavits of Support. Mexico does all filings online now. NOTICE: at this point a person can wait to file. The NVC will keep your case open as long as you contact them every year to let them know you are still not ready to file but want the case to remain open. This lets you control when you want the process to go forward again.
Third, once these forms are processed you’ll be scheduled for the first interview at the consulate. You have to schedule a medical exam at most consulates (a very few schedule them for you). In Mexico that also means you have to schedule a biometrics appointment and a medical exam. In Mexico you have the medical exam at a clinic days prior to your appointment and the cost for that can be anywhere from $100 to $400, depending on if immunizations or other treatments are needed. Some other consulates require the medical exam be done within different time limits.
Fourth, the first interview takes place where it is determined if the alien is either a) immediately eligible for a visa b) eligible to file a waiver, or c) not eligible to apply at all.
When someone is inadmissible but able to file a waiver the consulate gives (or should give) instructions on how to submit the I-601 waiver. (NOTICE: sometimes the consulate makes mistakes on inadmissibility or eligibility to file! This can cause problems.)
The waiver now is filed within the US at the Lockbox (centralized PO box) and sent to a service center for adjudication.
You have to wait for the Service center to adjudicate your case and inform you and/or your attorney as to the decision. Updates can be made if there are changes in your situation before the waiver is adjudicated.