Transaction Fees

Like most blockchains, Helium has a system of transaction fees. All transactions in the Helium blockchain are paid in Data Credits (DCs). Data Credits are produced via burning some amount of HNT using an on-chain transaction. And thanks to a system called "Implicit Burn", users (typically) don't need to manually supply DCs to pay fees. As long as the Helium wallet being used to submit the transaction contains enough HNT to burn to DCs to fund the transaction, the burn will happen implicitly, requiring no user intervention.

Transaction Fee Schedule

The following is a list of the current set of fees required for various transactions, along with their details. Transaction fees are paid in Data Credits. (Note that the cost is not shown in HNT as this number is variable based on the current $USD/HNT price as defined by the HNT Price Oracle.)

Fee Type	Fee Description	Cost (DC)	Cost ($USD)
Send HNT	Transferring HNT from wallet to wallet	`Variable`	`Variable`
Transferring Device Packet Data	Fee paid by device owner when sending or receiving sensor data. Metered per 24 bytes.	`1`	`$.00001`
Add Full Hotspot	Fee paid to add full Hotspot to the blockchain. Fee is generally covered by Hotspot maker.	`4000000`	`$40`
Add Data Only Hotspot	Fee paid to add a Data Only Hotspot to the blockchain.	`1000000`	`$10`
Assert Hotspot Location	Required when asserting a Hotspot's location. (The first assertions is generaly covered by Hotspot maker)	`1000000`	`$10`
Assert Data Only Location	Required for Optionally asserting a Data Only Hotspot's Location	`500000`	`$5`
Purchasing a blockchain OUI	Buy an OUI from the Helium blockchain	`10000000`	`$100`
Purchasing a blockchain Subnet	Buy a Subnet from the Helium blockchain	`10000000`	`$100`

Calculating the DC cost for Sending HNT

As noted above, the DC cost of a Send transaction is variable. The precise cost is based on the size of the transaction, in bytes. Once the size is calculated, we apply a 5000x multiplier. For a typical send transaction, where one wallet is sending to one wallet (like this one here), the complete transaction is made up of the following:

Transaction Component	Component Size (Bytes)
Payer Wallet Key	33
Payee Wallet Key	33
Payer Signature	64
Nonce	3 (approximate; ranges from 2-4)
Payment Amount	6 (approximate; ranges from 4-8)

In total, this is 139 bytes.
Each 24 bytes requires one Data Credit (as is the case when you're transferring device packet data).
139 / 24 results in 6 Data Credits.
We then apply our 5000x multiplier, and the result is a transaction fee
This results in a 30000 Data Credit cost for the above transaction.

Transaction Fees and Implicit Burn

The Helium blockchain uses something called implicit burn when paying fees.

Implicit Burn™

The term implicit burn was coined by Helium PM Coco "cokes" Tang, a recognized innovator in the blockchain technology and terminology space.

Thanks to Implicit Burn™, if you have enough HNT in your wallet to pay the transaction fee, the Helium Mobile Wallet (or the Helium Wallet CLI) will calculate the DC cost of your transaction and the blockchain will automatically burn the precise amount of HNT to supply the required DCs for the transaction. For example:

You need to send 10 HNT from a Helium Wallet that contains 11 HNT
The cost for this send transaction is 35000 DCs
Let's assume the HNT/$USD Oracle Price is $.35 at the time you send the HNT. This means that you'll need to supply a 1HNT to fund the 35000 DCs for this transaction.
When you send the 10 HNT, the Helium Wallet automatically supplies the 1 HNT to be burned into DCs.
After the transaction is submitted and processed, your resulting Helium Wallet balance will be 0 HNT.

In the above example, had you attempted to send 10.0001HNT with only 11 HNT in your wallet, this transaction would have failed as burning .999 HNT would only result in 34965 DCs, a mere 35 DCs short of the 35000 required for a send transaction.

Failed Transactions Result in No DCs Being Spent

Transactions in the Helium blockchain are atomic. In short, this means that they either succeed entirely or they don't. So, if you attempt to send HNT from a Helium Wallet without enough HNT to supply the required Data Credits, the transaction will fail after being submitted to the blockchain API by your wallet. And your HNT balance will be the same. No DCs were burned (or harmed) in this failed transaction.