# Transaction priority (/docs/internals/transaction-priority)

In Subtensor, transaction priority is determined by custom transaction extensions, which alter or override the default Substrate SDK behavior. Extensions affecting transaction priority are:

* **`ChargeTransactionPaymentWrapper`** (wraps `ChargeTransactionPayment`)
* **`DrandPriority`**

Substrate SDK combines priorities from all transaction extensions using addition.

## `ChargeTransactionPaymentWrapper` [#chargetransactionpaymentwrapper]

In the Substrate SDK, `ChargeTransactionPayment` normally calculates transaction priority based on:

* **Tip** — an extra fee paid by the sender.
* **Weight** — computational complexity of the transaction.
* **Dispatch class** — category of the transaction (`Normal`, `Operational`, `Mandatory`).

However, in Subtensor, `ChargeTransactionPaymentWrapper` **overrides** this logic.
It replaces the dynamic calculation with a **flat priority scale** based only on the dispatch class.

### Current priority values [#current-priority-values]

| Dispatch Class | Priority Value   | Notes                                                        |
| -------------- | ---------------- | ------------------------------------------------------------ |
| `Normal`       | `1`              | Standard transactions                                        |
| `Mandatory`    | `1`              | Rarely used, same as `Normal`                                |
| `Operational`  | `10_000_000_000` | Reserved for critical system extrinsics (e.g.: `sudo` calls) |

## `DrandPriority` [#drandpriority]

Special pallet\_drand priority: 10\_000 for `write_pulse` extrinsic.