Get-AzurePublicIPInventory

<#
.SYNOPSIS
    Inventories public IP addresses across the subscription.

.DESCRIPTION
    Lists every public IP address resource with what it is attached to,
    or flags it as unattached, since an unattached public IP still costs
    money and is easy to lose track of after a resource is deleted.

.EXAMPLE
    .\Get-AzurePublicIPInventory.ps1

.NOTES
    Requires the Az.Network module and an active Connect-AzAccount session.

.AUTHOR
    Shehryar Hassan
#>

$ips = Get-AzPublicIpAddress

$report = $ips | Select-Object Name, ResourceGroupName, IpAddress, Sku,
    @{N="Attached";E={[bool]$_.IpConfiguration}},
    @{N="AttachedTo";E={ if ($_.IpConfiguration) { ($_.IpConfiguration.Id -split "/")[-3] } else { "Unattached" } }}

$report | Format-Table -AutoSize
$unattached = $report | Where-Object { -not $_.Attached }
Write-Warning "$($unattached.Count) unattached public IP address(es) still provisioned."