Make sure IBAN's have their spaces removed.

app/Console/Commands/Correction/FixIbans.php

@@ -0,0 +1,50 @@
+<?php
+
+namespace FireflyIII\Console\Commands\Correction;
+
+use FireflyIII\Models\Account;
+use Illuminate\Console\Command;
+
+/**
+ * Class FixIbans
+ */
+class FixIbans extends Command
+{
+    /**
+     * The console command description.
+     *
+     * @var string
+     */
+    protected $description = 'Removes spaces from IBANs';
+    /**
+     * The name and signature of the console command.
+     *
+     * @var string
+     */
+    protected $signature = 'firefly-iii:fix-ibans';
+
+    /**
+     * Execute the console command.
+     *
+     * @return int
+     */
+    public function handle(): int
+    {
+        $accounts = Account::whereNotNull('iban')->get();
+        /** @var Account $account */
+        foreach ($accounts as $account) {
+            $iban = $account->iban;
+            if (str_contains($iban, ' ')) {
+
+                $iban = app('steam')->filterSpaces((string)$account->iban);
+                if ('' !== $iban) {
+                    $account->iban = $iban;
+                    $account->save();
+                    $this->line(sprintf('Removed spaces from IBAN of account #%d', $account->id));
+                }
+            }
+        }
+
+        return 0;
+    }
+}