INA 334(a) allows a person to file 3 months (also described as 90 days) ahead of reaching the 5 years LPR status required for filing under INA 316(a) or the 3 years LPR status required for filing under INA 319(a).
AND for Pete's sake (and your own sanity) wait a few days just to be on the safe side.
Note: The ONLY requirement that you can "cheat" on is the LPR status. AND it is ONLY for people applying based on the residence requirement under those sections of law.
It does NOT apply to people who broke residence and need to apply under the 4 years and 1 day rule or the 2 years and 1 day rule in 8 CFR 316.5(d)(1)(ii) after a break described in either (i) or (ii) of that CFR section.
It does not apply to anything else.
The FILING date locks you down on accumulating physical presence. Unless you have the required 30 or 18 months required inside the U.S. on the FILING DATE, you are out of luck.
On the FILING DATE the marriage had to have lasted a full three years (if filing based on marriage to a USC). This has to continue through Oath.
On the FILING DATE the spouse had to already be a USC for a full three years.
GMC (good moral charcter) has to be established for a FULL 3 or 5 years on the FILING DATE. This has to continue through Oath.
----I've heard of people who didn't understand that they needed to wait for a FULL 5 or 3 years AFTER that last conviction for petty theft or shoplifting or welfare fraud (CIMT) before they could file an N-400. "But they said I could file three months early......" It does not apply to anything but the LPR date.
----Crime Involving Moral Turpitude: an act which is base and vile.... (Something that makes you think the criminal is a low-life scum).
----Something can be a CIMT and something else (worse) like burglary, armed robbery, child molestation.......
----When something is more than JUST a CIMT...that person has bigger worries than N-400 eligibility. They'll be seeing an Immigration Judge instead.
TAX RETURNS:
If you indicated that you had ever failed to file taxes, the naturalization officer would ask for proof that you are currently OK with IRS, like a payment plan or filed an amended or late return and some proof of that.
If you have an approved N-470 under INA 316(b) that allowed you to work abroad for a U.S. employer, perhaps W-2's showing your employer information might be requested.
Tax returns are one of the items most often requested when you are filing based on a marriage to a USC. If you are NOT filing joint returns you better be able to explain the tax advantage in that decision.
Better proof is having a child or children together (preferably NOT while either of you was married to someone else--such as the USC spouse who immigrated your USC spouse--that smells like fraud...and forthcoming denaturalization).
