> ## Documentation Index
> Fetch the complete documentation index at: https://docs.base.org/llms.txt
> Use this file to discover all available pages before exploring further.

# Fees, Ordering, and Lifecycle

> Understand fees, expiry, and replacement for validity transactions.

## Fees

Transactions use the normal fee rules for their type. For EIP-1559 transactions, set `maxFeePerGas` and `maxPriorityFeePerGas` on the signed transaction.

A transaction that is not included does not pay onchain execution fees. An included transaction pays normal execution fees, even if it reverts.

## Ordering

A transaction competes for inclusion only after every predicate matches. A matching predicate does not reserve block space.

## Expiry

Add a `block_number` predicate with a maximum block to limit a transaction's lifetime. Combine it with `flashblock_index` to tighten the expiry bound to a position within that block's Flashblocks.

## Replacement

A later transaction with the same sender and nonce can replace a pending transaction. If the RPC returns an underpriced-replacement error, increase the fee fields, sign again, and retry.