Generate AzureAD B2B Pending and Accepted User Reports. Associated Blog Post can be found here https://blog.darrenjrobinson.com/azure-active-directory-b2b-pending-and-accepted-user-reports/

AzureAD B2B Pending & Accepted User Reports.ps1

# Adding the AD library for AuthN
Add-Type -Path 'C:\Program Files\WindowsPowerShell\Modules\AzureADPreview\2.0.0.52\Microsoft.IdentityModel.Clients.ActiveDirectory.dll'

# This is the tenant id of you Azure AD. You can use tenant name instead if you want.
$tenantID = "customer.onmicrosoft.com"
$authString = "https://login.microsoftonline.com/$tenantID" 

# The resource URI for your token.
$resource = "https://graph.microsoft.com/"

# This is the common client id.
$client_id = "1950a258-227b-4e31-a9cf-717495945fc2"

# Username and Password
$username = "user@domain.com.au"
$password = "p@$$w0rd1234"

# Output Path
$outPath = "C:\Reports"

# ********************** Authentication to Azure ***************************
# The username must be MFA disabled user Admin at least, and must not be a live id.
$creds = New-Object "Microsoft.IdentityModel.Clients.ActiveDirectory.UserCredential" `
                -ArgumentList $Username,$Password

# Create a authentication context with the above authentication string.
$authContext = New-Object "Microsoft.IdentityModel.Clients.ActiveDirectory.AuthenticationContext" `
                -ArgumentList $authString

# Acquire access token from server.
$authenticationResult = $authContext.AcquireToken($resource,$client_id,$creds)

# Use the access token to setup headers for your http request.
$authHeader = $authenticationResult.AccessTokenType + " " + $authenticationResult.AccessToken
$headers = @{"Authorization"=$authHeader; "Content-Type"="application/json"}

# Get first Page of Results for Accepted B2B Users
$B2BAccepted = Invoke-RestMethod -Uri "https://graph.microsoft.com/beta/users?filter=externalUserState eq 'Accepted'" -Headers $headers -Method Get
# Get first Page of Results for Pending B2B Users
$B2BPending = Invoke-RestMethod -Uri "https://graph.microsoft.com/beta/users?filter=externalUserState eq 'PendingAcceptance'" -Headers $headers -Method Get

$AcceptedObjects = @()
$PendingObjects = @()
# Add in our first objects
$AcceptedObjects += $B2BAccepted.value
$PendingObjects += $B2BPending.value
$moreAcceptedObjects = $B2BAccepted 
$morePendingObjects = $B2BPending 

# B2B Accepted
# Get all the remaining objects in batches if we didn't return them all already
if ($B2BAccepted.'@odata.nextLink'){
$moreAcceptedObjects.'@odata.nextLink' = $B2BAccepted.'@odata.nextLink'
do
{
    $moreObjects = Invoke-RestMethod -Method Get -Headers @{
    Authorization   = $authenticationResult.CreateAuthorizationHeader()
    'Content-Type'  = "application/json"
    } -Uri ($moreAcceptedObjects.'@odata.nextLink' -f $authenticationResult.TenantId)
    $moreObjects.value.count
    $AcceptedObjects += $moreObjects.value
    $AcceptedObjects.Count

} while ($moreObjects.'@odata.nextLink')
}

# B2B Pending
# Get all the remaining objects in batches if we didn't return them all already
$moreObjects = $null 
if ($B2BPending.'@odata.nextLink'){
    $morePendingObjects.'@odata.nextLink' = $B2BPending.'@odata.nextLink'
    do
    {
        $moreObjects = Invoke-RestMethod -Method Get -Headers @{
        Authorization   = $authenticationResult.CreateAuthorizationHeader()
        'Content-Type'  = "application/json"
        } -Uri ($morePendingObjects.'@odata.nextLink' -f $authenticationResult.TenantId)
        $moreObjects.value.count
        $PendingObjects += $moreObjects.value
        $PendingObjects.Count

    } while ($moreObjects.'@odata.nextLink')
}

$ReportTemplate = [pscustomobject][ordered]@{
    displayName = $null
    mail = $null
    accountEnabled = $null 
    createdDateTime = $null 
    externalUserStateChangeDateTime = $null
}

$cssStyle = '<style>body{background:#252525;font:87.5%/1.5em Lato,sans-serif;padding:20px}table{border-spacing:1px;border-collapse:collapse;background:#F7F6F6;border-radius:6px;overflow:hidden;max-width:800px;width:100%;margin:0 auto;position:relative}td,th{padding-left:8px}thead tr{height:60px;background:#367AB1;color:#F5F6FA;font-size:1.2em;font-weight:700;text-transform:uppercase}tbody tr{height:48px;border-bottom:1px solid #367AB1;text-transform:capitalize;font-size:1em;&:last-child {;border:0}tr:nth-child(even){background-color:#dae5f4;}tr:nth-child(odd){background:#b8d1f3;}</style>'


$pendingReport = @()
foreach ($pendingUser in $PendingObjects) {
    $pendingDate = $null
    $createdDate = $null 
    $pUser = $ReportTemplate.PsObject.Copy()
    $pendingDate = get-date($pendingUser.externalUserStateChangeDateTime)
    $createdDate = get-date($pendingUser.createdDateTime)
    write-host -foregroundcolor yellow "$($pendingUser.displayName) pending since $($pendingDate)"
    $pUser.accountEnabled = $pendingUser.accountEnabled
    $pUser.createdDateTime = $createdDate
    $pUser.displayName = $pendingUser.displayName
    $pUser.mail = $pendingUser.mail  
    $pUser.externalUserStateChangeDateTime = $pendingDate 
    $pendingReport += $puser 
}

$pendingReport | ConvertTo-Html -Body $cssStyle | Out-File "$($outPath)\PendingB2BUsers.html"

$acceptedReport = @()
foreach ($acceptedUser in $AcceptedObjects){
    $acceptedDate = get-date($acceptedUser.externalUserStateChangeDateTime)
    write-host -foregroundcolor Green "$($acceptedUser.displayName) accepted on $($acceptedDate)"
    $pendingDate = $null
    $createdDate = $null 
    $aUser = $ReportTemplate.PsObject.Copy()
    $pendingDate = get-date($acceptedUser.externalUserStateChangeDateTime)
    $createdDate = get-date($acceptedUser.createdDateTime)    
    $aUser.accountEnabled = $acceptedUser.accountEnabled
    $aUser.createdDateTime = $createdDate
    $aUser.displayName = $acceptedUser.displayName
    $aUser.mail = $acceptedUser.mail  
    $aUser.externalUserStateChangeDateTime = $pendingDate 
    $acceptedReport += $aUser 
}

$acceptedReport | ConvertTo-Html -Body $cssStyle | Out-File "$($outPath)\AcceptedB2BUsers.html"