What Is Bitcoin v3 Transaction Policy?

Definition

Bitcoin v3 transaction policy is the earlier implementation name for the node policy now commonly called TRUC, or Topologically Restricted Until Confirmation. It applies additional mempool and relay rules to unconfirmed transactions whose version field is 3. The policy limits dependency topology, transaction size, and replacement behavior to make fee bumping safer.

Overview

Meaning and scope

Mechanism and operation

Bitcoin v3 transaction policy refers to the policy framework that applies special relay and mempool restrictions to transactions with nVersion=3. The design was developed to improve anti-pinning properties and fee-bumping reliability for transaction protocols that must work with pre-signed or interdependent transactions. The name “v3 policy” appeared during development, while BIP 431 standardized the more descriptive term Topologically Restricted Until Confirmation, or TRUC. A participating transaction is expected to have only a limited parent-child structure, and connected unconfirmed transactions must also use the policy. Additional virtual-size limits reduce how much low-feerate or high-absolute-fee data can be attached to a transaction package.

Practical payment example

A Bitcoin fee-bumping implementation tests whether a candidate package obeys version-three topology and size rules before broadcasting.

Operational checks

Replacement and sibling-eviction rules can then evaluate a smaller, bounded structure instead of an unrestricted dependency graph. A transaction may therefore be valid for inclusion in a block while being nonstandard or rejected by a particular node’s local policy. For current documentation and implementation work, TRUC is the clearer name because it describes the temporary restriction that lasts until confirmation.

Distinctions and limits

The number 3 is stored in the transaction version field, but the policy should not be confused with a consensus-level transaction type. Bitcoin blocks can contain transactions that nodes did not previously relay through their own mempools, provided those transactions satisfy consensus rules.

Related definitions: transaction, transaction type.

Example