TEP-8: Expire Function

Abstract

This proposal introduces a single new function, expire, to the Accounting Subnet defined in TEP-6. The expire function allows subnets and applications to invalidate or burn a user's credits in a controlled and auditable manner.

This mechanism is designed to support external subscription and credit systems where applications manage their own lifecycle logic but require a standardized way to mark remaining balances as expired.

Motivation

While TEP-6 provides the primitives for crediting and debiting user balances, it does not offer a protocol-level method for expiring unused credits. Many applications and subnets employ custom subscription models, prepaid credits, or time-limited offers that require explicit balance invalidation.

The addition of an expire function ensures:

• A standardized, auditable way to mark credits as expired or removed.
• Reduced reliance on ad-hoc adjustments, minimizing errors and disputes.
• Better compatibility with applications that manage subscriptions or prepaid balances externally.

Specification

The Accounting Subnet is extended with a single new function:

expire

The expire function invalidates a user's total balance. It is intended to be called by subnets or applications that determine a user's credits have reached the end of their lifecycle (e.g., due to a subscription expiration, trial end, or service deactivation).

Parameters

• user : the user address or identifier whose balance will be reduced.
• currency : the currency or token type (e.g., KNS, USDC).
• signature : a signed payload verifying that the expiration request is authorized by the subnet or protocol authority.

Behavior

• The expire function sets the user's balance to zero in the Accounting Subnet.
• The function fails if the signature is invalid.

Rationale

Adding only expire keeps the protocol simple and aligned with TEP-6 design. It allows subnets and apps to control their own subscription or credit models, while using a unified protocol function to enforce expirations. This minimizes complexity, avoids imposing rigid lifecycle rules, and ensures accurate and auditable balance management.

Backwards Compatibility

This proposal is fully backwards compatible. Subnets and apps that do not require expiration can continue to rely solely on credit and debit.

Reference Implementation

A reference implementation of expire will be added to the Accounting Subnet, with the same signature validation and event logging mechanisms used for debit.

References

TEP-6: Fee Mechanism