A citation to the Code of Federal Regulations can tell you which rule VA says it is applying. It is most useful when you connect it to the reason given for the decision.

The tables below cover twenty regulations that address common disability-claim questions. They are selected for their usefulness, not ranked as the twenty rules behind every decision.

A regulation cited as “38 C.F.R.” is different from a statute cited as “38 U.S.C.” The letters are not alternate spellings of the same authority. For example, 38 U.S.C. § 5103A is a statute addressing assistance, while 38 C.F.R. § 3.159 implements important notice and assistance requirements.

Evidence and the decision process

RegulationWhat it helps you understand
§ 3.102Reasonable doubt; it does not require an award whenever two pieces of evidence disagree
§ 3.103Procedural protections and notice, including opportunities to participate in the claim process
§ 3.104Binding decisions and favorable findings, subject to the applicable exceptions
§ 3.105Certain revisions of decisions and proposed adverse actions, including different standards and procedures for different actions
§ 3.159Evidence, notice and VA's duty to assist, with requirements that depend on the claim and review setting

A favorable finding can narrow a dispute. It does not mean every related fact is permanently beyond review under all circumstances. Likewise, “duty to assist” does not mean every review lane accepts new evidence or develops it in the same way.

When you read a denial, separate a missing-evidence problem from a disagreement about the weight VA gave evidence already present. That difference can affect the appropriate next step.

Establishing service connection

RegulationWhat it helps you understand
§ 3.303Principles of service connection, including conditions diagnosed after discharge when the evidence establishes the relationship
§ 3.304Additional direct-service-connection rules, including specific provisions for PTSD and the presumption of soundness
§ 3.307Conditions and service requirements for certain presumptions
§ 3.309Disease lists for specified presumptive frameworks
§ 3.310Secondary service connection through causation or aggravation

These sections answer different questions. A condition's absence from one presumptive list does not automatically dispose of every direct or secondary theory. Conversely, a diagnosis alone does not show that a veteran meets the service requirements for a particular presumption.

Our map of service-connection types can help organize those possibilities. Use the actual rule and facts rather than treating the categories as interchangeable.

Dates and review choices

RegulationWhat it helps you understand
§ 3.400General effective-date rules and exceptions; it is not a promise of payment back to the first symptom
§ 3.2501Supplemental Claims and new and relevant evidence
§ 3.2601Higher-Level Review, generally using the evidence of record at the prior decision

Section 3.2501 is the Supplemental Claim rule. It is not the Higher-Level Review rule. That distinction matters if you have a new medical opinion you want VA to consider.

A Supplemental Claim and Higher-Level Review are not interchangeable ways to submit the same packet. Read VA's comparison of review options and the instructions accompanying your decision. The available choices and deadlines depend on what VA decided and which system applies.

Evaluating the level of disability

RegulationWhat it helps you understand
§ 4.1The general purpose of the rating schedule and the importance of disability history
§ 4.3Resolution of reasonable doubt about the degree of disability
§ 4.7Choosing between two evaluations when the disability picture more nearly approximates one set of criteria
§ 4.14Avoiding duplicate compensation for the same disability manifestations, often called pyramiding

The diagnosis and the rating criteria both matter. A percentage available for one diagnostic code is not necessarily available for another. Several diagnoses also do not automatically justify separate compensation for overlapping manifestations.

What the Board can consider and what its decision means

RegulationWhat it helps you understand
§ 20.301The evidence record for a modernized Board appeal on the Direct Review docket
§ 20.303Evidence Submission docket: evidence submitted with the appeal or within the specified 90-day window, in addition to the applicable earlier record
§ 20.1303The nonprecedential nature of individual Board decisions

Section 20.1303 does not set the general finality rule for all decisions. It explains why another veteran's Board award does not bind the Board to grant a similar-looking claim.

The Direct Review and Evidence Submission rules concern different evidentiary records. Mailing an important document does not ensure it will be considered in a window where the Board cannot accept it. Check the chosen docket and notice before submitting additional evidence.

Read the version that applies to the period

The links above open the current regulation. A historical rating or an allegation of error in an old decision may require the version in effect at the relevant time. Changes to a diagnostic code or procedure can make a present-day summary unsuitable for an earlier period.

The eCFR provides regulation text and version information; GovInfo's CFR collection preserves annual editions. The decision's date and the benefit period are important context when selecting the source.

Source and method

I selected these twenty sections by the questions they address. The original extraction data contain citation variants and repeated condition records, so this article makes no claim that these are the twenty most frequently cited unique authorities. It is a guide for locating and understanding rules, not individualized legal advice. Sources reviewed September 16, 2026.