The non-refundable storage fee isn’t exactly 1% of the storage rebate because it’s calculated using the network’s defined rebate rate and storage gas price, not a simple percentage formula. The 1% figure you may have heard is more of an approximation for certain scenarios, but in practice, the fee comes from (Storage Rebate × (1 - Rebate Rate/10000)) adjusted by the storage gas price. In your case, the rebate rate is 9900 (which means 99% rebate), and the storage gas price factor changes the final value, so it doesn’t match a flat 1% of the rebate. This ensures the network retains a minimal fee to prevent abuse and cover baseline storage costs.

You can read more on how storage fees are calculated here: Sui Gas and Storage Costs Explained

Example calculation block based on your data:

# Formula: Non-Refundable Storage Fee = Storage Rebate × (1 - RebateRate/10000)
# Given: Storage Rebate = 13031568, RebateRate = 9900 (99%)
Fee = 13031568 * (1 - 0.99) 
Fee = 130315.68  # ~ matches your 131632 due to rounding/storage gas adjustments

The non-refundable storage fee in your Sui transaction isn't exactly 1% of the storage rebate because it's actually taken as 1% of the full original storage cost from when the data was first added, not just the refunded part you get back. When you remove or update stored items, Sui gives you back 99% of that initial cost as the rebate, keeping the other 1% to help with the network's long-term upkeep. In your case, adding up the rebate of 13,031,568 and the fee of 131,632 gives the original storage value of 13,163,200, and 1% of that matches your fee spot on, while calculating 1% off the rebate alone would give about 130,316, which doesn't line up. The rebate rate of 9,900 out of 10,000 backs this up, showing it's set at 99% return. This system motivates folks to clear out old data while ensuring the network has funds for ongoing costs.

Why the Non-Refundable Storage Fee ≠ 1% of Storage Rebate

I’m trying to understand this aspect of the Sui Network because I’m either building, debugging, or deploying something that touches this area. I want a detailed explanation of how this mechanism or feature works, along with relevant CLI usage, Move code structure, or architectural concepts. My goal is to gain enough clarity to apply this knowledge in a real project—whether that’s a custom smart contract, an NFT system, a wallet integration, or a DeFi tool. The Sui Network has unique features compared to EVM chains, so I’m particularly interested in what sets it apart and how that affects development best practices. It would help to have sample code, command line examples, or typical errors to watch for, especially when using the Sui CLI, SDK, or deploying on localnet/testnet. Ultimately, I want to avoid common mistakes, follow the best security principles, and ensure that the functionality I’m working on behaves as expected under realistic conditions.

🔹 The Storage Model in Sui

• Every object stored on-chain consumes Storage Gas Units (SGUs).
• When you create or mutate objects, you pay a Storage Cost.
• If objects are later deleted, you receive a Storage Rebate — but not the full cost.
• A small percentage is kept back permanently as a Non-Refundable Storage Fee, which funds long-term storage and protocol sustainability.

🔹 Why It’s Not Exactly 1%

Looking at your numbers:

• Storage Cost = 11,187,200
• Storage Rebate = 13,031,568
• Non-Refundable Fee = 131,632

At first glance, you might expect:

Non-Refundable Fee = 1% of Storage Rebate
= 130,315

But your fee is 131,632, slightly higher.

This happens because:

1. Fee is computed on Storage Gas Units, not the raw rebate in MIST.

   • The rebate and fee are both derived from the SGU schedule and the current Storage Gas Price (76 in your table).

2. Rounding effects: When converting from SGUs → MIST, integer math causes rounding differences. These usually show up as a few hundred/thousand MIST difference.

3. Protocol parameters: The fee is calculated as rebate_rate / 10000 of the storage rebate, where rebate_rate here is 9900. This means you only get 99% rebate, but the actual deduction uses internal integer division.

So the "1% rule" is conceptual, but in practice, the actual non-refundable fee is slightly adjusted by integer math and SGU conversion.

🔹 CLI / SDK Verification

You can inspect how Sui calculates it using the CLI:

sui client dry-run-tx --tx <your_tx_id>

This outputs the same GasInfo block you shared, showing the breakdown of computation, storage, rebate, and fee.

If coding in TypeScript:

const res = await provider.devInspectTransactionBlock({
  transactionBlock: tx,
  sender: walletAddress,
});

console.log(res.effects.gasUsed);

This will show the same storage_rebate and non_refundable_storage_fee values.

🔹 Best Practices

• Never hard-code “1%” in your dApp logic. Always read from transaction effects.
• When building refund/escrow systems, use the actual on-chain storage_rebate field, not an assumed percentage.
• Test on localnet with varying storage_gas_price to see how small rounding deviations appear.

The Non-Refundable Storage Fee is not strictly 1% of the Storage Rebate because it is calculated based on the net storage cost after applying the rebate rate (e.g., 99% refundable, 1% non-refundable) to the original storage cost, not the rebate amount itself. In your example, the rebate rate is 9900 (99%), meaning 1% of the initial storage cost is withheld as a fee—not 1% of the rebate. The formula is:
Non-Refundable Fee = Storage Cost × (1 - Rebate Rate / 10000).
Here, 11187200 × (1 - 9900/10000) = 11187200 × 0.01 = 111872 (close to 131632, with minor rounding or tier adjustments). Sui’s gas model prioritizes predictability, so fees scale with resource usage, not the rebate.

The Non-Refundable Storage Fee is 1% of the Storage Cost (not the Rebate).

In your example:

• Storage Cost: 11,187,200
• 1% Fee: ~111,872 (close to your 131,632, likely due to rounding or gas price adjustments)

Why?
Sui charges a small fee to prevent spam—it’s deducted from the rebate you’d otherwise get.

Formula:
Non-Refundable Fee ≈ (Storage Cost * 1%)

(It incentivizes efficient storage cleanup.)

That's a sharp observation. The math doesn't seem to line up, and it's not just you—it's a bit confusing.

The non-refundable storage fee isn't a simple 1% of the rebate. It's actually 1% of the total storage cost before the rebate is applied. So in your case, it's 1% of that 11,187,200 figure.

Let me do that quick math: 1% of 11,187,200 is 111,872. But your fee is 131,632, which is higher. That's where the Rebate Rate of 9900 (or 99%) comes in. The system keeps 1% of the storage cost as a fee, but the calculation gets adjusted by this rebate rate.

Honestly, the exact formula is more complex under the hood. The key takeaway is that it's a small fee on the storage you use, not a direct cut of your rebate. The numbers can look off at first glance. I had to dig through the docs to get this myself.