Transaction Underpriced Error

This error usually happens when the transaction's specified fee does not satisfy the minimum network requirements for execution.

On Neo X, transaction fees are composed of two parts: the base fee, which is burned, and the gas tip, which serves as an incentive distributed to governance nodes and voters. The base fee is fixed and independent of transaction volume. The gas tip is user-defined and can be adjusted. However, the Neo X network policy mandates a minimum value (20 gwei) for the gas tip. Transactions that do not meet the minimum gas tip requirement will be rejected.

According to EIP-1559, users determine their desired gas tip (gasTipCap) and the total fee they are willing to pay (gasFeeCap). The gas fee cap must cover both the base fee and the gas tip.

If the gasTipCap is too low, the transaction will be flagged as underpriced. Similarly, if the gasFeeCap is insufficient, the transaction will fail.

Error Context

A typical error message looks like this:

- server returned an error response: error code -32000: transaction underpriced: policy minGasTipCap needed 20000000000, baseFee needed 20000000000, gasTipCap 1, gasFeeCap 40000000001

• minGasTipCap: The minimum gas tip (priority fee) required by the network.

• baseFee: The network base fee. Currently it is 20 gwei for Neo X.

• gasTipCap: The user-specified priority fee offered to incentivize miners or validators.

• gasFeeCap: The total fee the user is willing to pay, which covers both the base fee and gas tip.

Solution

To resolve this issue, ensure that the transaction fees meet the following conditions:

• gasTipCap >= minGasTipCap (e.g., 20 gwei for Neo X).

• gasFeeCap >= baseFee (e.g., 20 gwei) + minGasTipCap.