Use ReleaseAddress with an AWS SDK or CLI

    /// <summary>
    /// Release an Elastic IP address. After the Elastic IP address is released,
    /// it can no longer be used.
    /// </summary>
    /// <param name="allocationId">The allocation Id of the Elastic IP address.</param>
    /// <returns>True if successful.</returns>
    public async Task<bool> ReleaseAddress(string allocationId)
    {
        try
        {
            var request = new ReleaseAddressRequest { AllocationId = allocationId };

            var response = await _amazonEC2.ReleaseAddressAsync(request);
            return response.HttpStatusCode == HttpStatusCode.OK;
        }
        catch (AmazonEC2Exception ec2Exception)
        {
            if (ec2Exception.ErrorCode == "InvalidAllocationID.NotFound")
            {
                _logger.LogError(
                    $"AllocationId {allocationId} was not found. {ec2Exception.Message}");
            }

            return false;
        }
        catch (Exception ex)
        {
            _logger.LogError(
                $"An error occurred while releasing the AllocationId {allocationId}.: {ex.Message}");
            return false;
        }
    }

###############################################################################
# function ec2_release_address
#
# This function releases an Elastic IP address from an Amazon Elastic Compute Cloud (Amazon EC2) instance.
#
# Parameters:
#       -a allocation_id - The allocation ID of the Elastic IP address to release.
#
# Returns:
#       0 - If successful.
#       1 - If it fails.
#
###############################################################################
function ec2_release_address() {
  local allocation_id response

  # Function to display usage information
  function usage() {
    echo "function ec2_release_address"
    echo "Releases an Elastic IP address from an Amazon Elastic Compute Cloud (Amazon EC2) instance."
    echo "  -a allocation_id - The allocation ID of the Elastic IP address to release."
    echo ""
  }

  # Parse the command-line arguments
  while getopts "a:h" option; do
    case "${option}" in
      a) allocation_id="${OPTARG}" ;;
      h)
        usage
        return 0
        ;;
      \?)
        echo "Invalid parameter"
        usage
        return 1
        ;;
    esac
  done
  export OPTIND=1

  # Validate the input parameters
  if [[ -z "$allocation_id" ]]; then
    errecho "ERROR: You must provide an allocation ID with the -a parameter."
    return 1
  fi

  response=$(aws ec2 release-address \
    --allocation-id "$allocation_id") || {
    aws_cli_error_log ${?}
    errecho "ERROR: AWS reports release-address operation failed."
    errecho "$response"
    return 1
  }

  return 0
}

The utility functions used in this example.

###############################################################################
# function errecho
#
# This function outputs everything sent to it to STDERR (standard error output).
###############################################################################
function errecho() {
  printf "%s\n" "$*" 1>&2
}

##############################################################################
# function aws_cli_error_log()
#
# This function is used to log the error messages from the AWS CLI.
#
# The function expects the following argument:
#         $1 - The error code returned by the AWS CLI.
#
#  Returns:
#          0: - Success.
#
##############################################################################
function aws_cli_error_log() {
  local err_code=$1
  errecho "Error code : $err_code"
  if [ "$err_code" == 1 ]; then
    errecho "  One or more S3 transfers failed."
  elif [ "$err_code" == 2 ]; then
    errecho "  Command line failed to parse."
  elif [ "$err_code" == 130 ]; then
    errecho "  Process received SIGINT."
  elif [ "$err_code" == 252 ]; then
    errecho "  Command syntax invalid."
  elif [ "$err_code" == 253 ]; then
    errecho "  The system environment or configuration was invalid."
  elif [ "$err_code" == 254 ]; then
    errecho "  The service returned an error."
  elif [ "$err_code" == 255 ]; then
    errecho "  255 is a catch-all error."
  fi

  return 0
}

//! Release an Elastic IP address.
/*!
  \param clientConfiguration: AWS client configuration.
  \return bool: Function succeeded.
 */
bool AwsDoc::EC2::releaseAddress(const Aws::String &allocationID,
                                 const Aws::Client::ClientConfiguration &clientConfiguration) {
    Aws::EC2::EC2Client ec2(clientConfiguration);

    Aws::EC2::Model::ReleaseAddressRequest request;
    request.SetAllocationId(allocationID);

    Aws::EC2::Model::ReleaseAddressOutcome outcome = ec2.ReleaseAddress(request);
    if (!outcome.IsSuccess()) {
        std::cerr << "Failed to release Elastic IP address " <<
                  allocationID << ":" << outcome.GetError().GetMessage() <<
                  std::endl;
    } else {
        std::cout << "Successfully released Elastic IP address " <<
                  allocationID << std::endl;
    }

    return outcome.IsSuccess();
}

To release an Elastic IP addresses for EC2-Classic

This example releases an Elastic IP address for use with instances in EC2-Classic. If the command succeeds, no output is returned.

Command:

aws ec2 release-address --public-ip 198.51.100.0

To release an Elastic IP address for EC2-VPC

This example releases an Elastic IP address for use with instances in a VPC. If the command succeeds, no output is returned.

Command:

aws ec2 release-address --allocation-id eipalloc-64d5890a

    /**
     * Releases an Elastic IP address asynchronously.
     *
     * @param allocId the allocation ID of the Elastic IP address to be released
     * @return a {@link CompletableFuture} representing the asynchronous operation of releasing the Elastic IP address
     */
    public CompletableFuture<ReleaseAddressResponse> releaseEC2AddressAsync(String allocId) {
        ReleaseAddressRequest request = ReleaseAddressRequest.builder()
            .allocationId(allocId)
            .build();

        CompletableFuture<ReleaseAddressResponse> response = getAsyncClient().releaseAddress(request);
        response.whenComplete((resp, ex) -> {
            if (ex != null) {
                throw new RuntimeException("Failed to release Elastic IP address", ex);
            }
        });

        return response;
    }

import { ReleaseAddressCommand, EC2Client } from "@aws-sdk/client-ec2";

/**
 * Release an Elastic IP address.
 * @param {{ allocationId: string }} options
 */
export const main = async ({ allocationId }) => {
  const client = new EC2Client({});
  const command = new ReleaseAddressCommand({
    // You can also use PublicIp, but that is for EC2 classic which is being retired.
    AllocationId: allocationId,
  });

  try {
    await client.send(command);
    console.log("Successfully released address.");
  } catch (caught) {
    if (
      caught instanceof Error &&
      caught.name === "InvalidAllocationID.NotFound"
    ) {
      console.warn(`${caught.message}. Please provide a valid AllocationID.`);
    } else {
      throw caught;
    }
  }
};

suspend fun releaseEC2AddressSc(allocId: String?) {
    val request =
        ReleaseAddressRequest {
            allocationId = allocId
        }

    Ec2Client { region = "us-west-2" }.use { ec2 ->
        ec2.releaseAddress(request)
        println("Successfully released Elastic IP address $allocId")
    }
}

Example 1: This example releases the specified Elastic IP address for instances in a VPC.

Remove-EC2Address -AllocationId eipalloc-12345678 -Force

Example 2: This example releases the specified Elastic IP address for instances in EC2-Classic.

Remove-EC2Address -PublicIp 198.51.100.2 -Force

class ElasticIpWrapper:
    """Encapsulates Amazon Elastic Compute Cloud (Amazon EC2) Elastic IP address actions using the client interface."""

    class ElasticIp:
        """Represents an Elastic IP and its associated instance."""

        def __init__(
            self, allocation_id: str, public_ip: str, instance_id: Optional[str] = None
        ) -> None:
            """
            Initializes the ElasticIp object.

            :param allocation_id: The allocation ID of the Elastic IP.
            :param public_ip: The public IP address of the Elastic IP.
            :param instance_id: The ID of the associated EC2 instance, if any.
            """
            self.allocation_id = allocation_id
            self.public_ip = public_ip
            self.instance_id = instance_id

    def __init__(self, ec2_client: Any) -> None:
        """
        Initializes the ElasticIpWrapper with an EC2 client.

        :param ec2_client: A Boto3 Amazon EC2 client. This client provides low-level
                           access to AWS EC2 services.
        """
        self.ec2_client = ec2_client
        self.elastic_ips: List[ElasticIpWrapper.ElasticIp] = []

    @classmethod
    def from_client(cls) -> "ElasticIpWrapper":
        """
        Creates an ElasticIpWrapper instance with a default EC2 client.

        :return: An instance of ElasticIpWrapper initialized with the default EC2 client.
        """
        ec2_client = boto3.client("ec2")
        return cls(ec2_client)


    def release(self, allocation_id: str) -> None:
        """
        Releases an Elastic IP address. After the Elastic IP address is released,
        it can no longer be used.

        :param allocation_id: The allocation ID of the Elastic IP to release.
        :raises ClientError: If the release fails, such as when the Elastic IP address is not found.
        """
        elastic_ip = self.get_elastic_ip_by_allocation(self.elastic_ips, allocation_id)
        if elastic_ip is None:
            logger.info(f"No Elastic IP found with allocation ID {allocation_id}.")
            return

        try:
            self.ec2_client.release_address(AllocationId=allocation_id)
            self.elastic_ips.remove(elastic_ip)  # Remove the Elastic IP from the list
        except ClientError as err:
            if err.response["Error"]["Code"] == "InvalidAddress.NotFound":
                logger.error(
                    f"Failed to release Elastic IP address {allocation_id} "
                    "because it could not be found. Verify the Elastic IP address "
                    "and ensure it is allocated to your account in the correct region "
                    "before attempting to release it."
                )
            raise

# Releases an Elastic IP address from an
# Amazon Elastic Compute Cloud (Amazon EC2) instance.
#
# Prerequisites:
#
# - An Amazon EC2 instance with an associated Elastic IP address.
#
# @param ec2_client [Aws::EC2::Client] An initialized EC2 client.
# @param allocation_id [String] The ID of the allocation corresponding to
#   the Elastic IP address.
# @return [Boolean] true if the Elastic IP address was released;
#   otherwise, false.
# @example
#   exit 1 unless elastic_ip_address_released?(
#     Aws::EC2::Client.new(region: 'us-west-2'),
#     'eipalloc-04452e528a66279EX'
#   )
def elastic_ip_address_released?(ec2_client, allocation_id)
  ec2_client.release_address(allocation_id: allocation_id)
  true
rescue StandardError => e
  puts("Error releasing Elastic IP address: #{e.message}")
  false
end

    pub async fn deallocate_ip_address(&self, allocation_id: &str) -> Result<(), EC2Error> {
        self.client
            .release_address()
            .allocation_id(allocation_id)
            .send()
            .await?;
        Ok(())
    }

    TRY.
        lo_ec2->releaseaddress( iv_allocationid = iv_allocation_id ).
        MESSAGE 'Elastic IP address released.' TYPE 'I'.
      CATCH /aws1/cx_rt_service_generic INTO DATA(lo_exception).
        DATA(lv_error) = |"{ lo_exception->av_err_code }" - { lo_exception->av_err_msg }|.
        MESSAGE lv_error TYPE 'E'.
    ENDTRY.