You have one year. The effective date clock starts the day the letter is dated.
Under 38 CFR 3.2500, you have exactly one year from the date on the VA decision letter to file any of the three appeal lanes. Miss that date and the decision becomes final — you can still file a new claim, but you lose the original effective date and any retroactive backpay tied to it.
Continuous pursuit means staying in the system without letting any response deadline lapse. If you file a Supplemental Claim within one year of denial, and that Supplemental Claim is denied, you then have one year from that decision to file the next lane — and so on, all the way to BVA and federal court. As long as you never let a deadline run, your original effective date travels with the claim.
This is why a veteran who first filed in 2019, got denied, filed a Supplemental Claim in 2020, got denied again, and filed a BVA Notice of Disagreement in 2021 — and finally won at BVA in 2024 — gets paid all the way back to 2019. That's up to 5 years of retroactive compensation for a 30% rating. The year-by-year compounding of unpaid backpay is why continuous pursuit matters.
If you let the year run out: effective date resets to the date of your next filing. The lost months are gone. There is no waiver process and no equitable exception for most cases. File any lane before the deadline — even a Supplemental Claim with a single piece of new evidence — to stay in pursuit. See: 38 CFR 3.2500 at eCFR.
The one-year clock runs from the date printed on the VA decision letter, not the postmark and not the day you opened it. If the letter is dated January 15 and you didn't receive it until January 22, your deadline is still January 15 of the following year. Request a copy of every decision through VA.gov or through your VSO immediately — don't rely on delivery tracking.