A decision is a starting point, not a verdict. These are the moves still open to you, in the order they matter, the ones with a clock on them first.
The date on your decision letter starts a one-year clock. Within that year you can ask for a Higher-Level Review, file a Supplemental Claim with new evidence, or appeal to the Board, and your original effective date is preserved. Let the year lapse and a later claim starts from the new filing date instead, which is where most of the money is lost.
A decision is also worth re-reading for what it did not do. Conditions rated at 0% are still service-connected and can be increased later. TDIU has to be considered whenever the evidence raises it. SMC-K is paid on top of the schedule and is routinely missed. Dependents added to an award are backdated if you claim them in time. None of that is automatic.
There are three ways back in, and they are not interchangeable. A Higher-Level Review asks a senior rater to look at the same evidence again and is the right lane when you believe the rules were applied wrongly to what was already in the file; no new evidence is allowed. A Supplemental Claim is the lane when you have something new, a fresh diagnosis, a nexus letter, buddy statements, and it is the most commonly successful of the three. A Board appeal goes to a Veterans Law Judge and takes far longer, but it is the only route to a hearing.
Read the decision itself before choosing. The reasons and bases section states which criteria the rater found met and which they did not, and that is the specific gap any new evidence has to close. An effective date that does not match your Intent to File, a condition that was granted but rated at 0% when the criteria for 10% look met, or a claim where unemployability was raised and never addressed are all worth challenging, and all are easy to miss on a first read.
Educational only, not legal advice and not a VA determination. Confirm every date against your decision letter and
VA.gov decision reviews.