Storage Rebate

A Storage Rebate is a refund of the gas fees originally paid to store data on-chain. It is returned to the transaction sender when an object is deleted or mutated to a smaller size, effectively freeing up global storage. This creates a direct financial incentive for users to clean up unused data.

The rebate pool is pre-funded. When an object is first created, a portion of the paid gas fee is earmarked as a future rebate and stored within the object itself. This ensures the funds for the eventual refund are guaranteed and cannot be spent by the network.

To prevent spam from micro-rebates, Sui implements a dust collector. Small, unclaimed rebates below a threshold (e.g., from deleting tiny objects) are not sent to users. Instead, they are periodically aggregated and burned, removing them from circulation and providing deflationary pressure.

Unlike storage rent models (e.g., Ethereum's state rent proposal), which charge ongoing fees, Sui's rebate is a one-time refund. Users pay upfront for storage and get reimbursed upon deletion, aligning incentives for both allocation and cleanup without recurring costs.

Storage rebates are integral to Sui's gas fee model. The gas price covers computation, bandwidth, and storage. The storage portion is split: one part is burned for computation/bandwidth, and the remainder is reserved for the rebate. This design aims for net-zero storage cost for responsible users.

For developers, rebates are handled automatically by the Sui runtime. To receive a rebate, a transaction must explicitly delete an object (e.g., using sui::transfer::delete or sui::coin::burn). The rebate is then added to the gas coin balance of the transaction sender.

The primary goal is to encourage users to delete obsolete data from the blockchain state. By offering a partial refund of the original storage cost, it makes it economically rational for users to delete objects or close accounts they no longer need, rather than leaving them to bloat the network indefinitely.

When a user initially stores data, they pay a storage fee as part of the transaction gas. The rebate system tracks this fee. When the data is later deleted, a portion of that fee is returned to the entity that pays for the deletion transaction, acting as a gas subsidy for the cleanup operation.

Without a rebate, there is a direct economic disincentive to delete data, as doing so costs gas but provides no immediate user benefit. Rebates counteract this by making storage a revolving resource. This is critical for long-term scalability, as it helps manage the growth of the global state that all nodes must store and process.

The mechanism creates an alignment between individual user incentives and the overall health of the network. Users are financially rewarded for actions that benefit the collective by reducing the state size, turning a public good (clean state) into a private good (a rebate).

By reducing the net cost of temporary storage, rebates enable new application designs. For example, gas-less transactions can be facilitated by sponsors who are later reimbursed, or temporary data caches can be used on-chain with predictable, lower net costs.

A storage rebate is distinct from storage rent (a recurring fee to keep data alive). Rebates are a one-time refund upon deletion. Some networks use a hybrid model: charging rent for long-term storage and offering rebates to incentivize deletion, creating a complete economic system for state management.

Gas fees are the primary transaction cost on blockchains like Ethereum and Sui, paid to validators for computation and execution. A storage rebate is a distinct, refundable component of the total gas fee, specifically compensating users for freeing up on-chain storage. This creates a direct economic incentive for state cleanup.

State bloat refers to the uncontrolled growth of data stored permanently on a blockchain, which increases hardware requirements for nodes and slows network performance. Storage rebates are a counter-mechanism designed to mitigate state bloat by financially rewarding users who delete obsolete data, such as spent UTXOs or deleted smart contract objects.

Storage rent is a periodic fee charged for the ongoing cost of data storage on-chain. Unlike a one-time rebate, rent is a continuous cost. Systems like Solana's and Ethereum's EIP-1559 (which burns base fee) address similar state sustainability issues but through different economic models—ongoing taxation versus a one-time refund upon deletion.

In the Sui Move programming model, data is represented as distinct, ownable objects. Storage rebates are intrinsically linked to this model. When an object is deleted (e.g., merging coins, closing a marketplace listing), the object owner receives a rebate for the storage space reclaimed, directly tying economic incentives to the data structure.

The net gas price is the final cost a user pays for a transaction after accounting for all rebates and refunds. It is calculated as:

• Total Gas Cost (computation + storage) - Storage Rebate. This means a transaction that deletes more data than it creates can result in a negative net cost, effectively paying the user.

Storage reclamation is the process of freeing up allocated but unused blockchain storage. A rebate is the economic trigger for this process. Without such incentives, orphaned data persists indefinitely, forcing networks to rely on less efficient or centralized garbage collection protocols. Rebates automate cleanup via user self-interest.