diff --git a/app/app/Services/Billing/BalancePreflightService.php b/app/app/Services/Billing/BalancePreflightService.php
new file mode 100644
index 00000000..b56249f1
--- /dev/null
+++ b/app/app/Services/Billing/BalancePreflightService.php
@@ -0,0 +1,49 @@
+<?php
+
+declare(strict_types=1);
+
+namespace App\Services\Billing;
+
+use App\Models\PricingTier;
+use Illuminate\Database\Eloquent\Collection;
+
+/**
+ * Pure: проходит ли клиент преfflight — хватает ли баланса на ПОЛНЫЙ дневной
+ * лимит всех его eligible-проектов по текущему тарифу.
+ *
+ * Сравнение в ЛИДАХ (capacity vs required), не в рублях — переиспользует
+ * BalanceToLeadsConverter::convert, который учитывает 7 ступеней и накопленный
+ * месячный объём (deliveredInMonth).
+ *
+ * Spec: docs/superpowers/specs/2026-05-24-billing-v2-spec-c-preflight-vtb-design.md §3.3
+ */
+final class BalancePreflightService
+{
+    public function __construct(
+        private readonly BalanceToLeadsConverter $converter = new BalanceToLeadsConverter,
+    ) {}
+
+    /**
+     * @param  Collection<int, PricingTier>  $tiers
+     */
+    public function evaluate(
+        string $balanceRub,
+        int $deliveredInMonth,
+        int $requiredLeads,
+        Collection $tiers,
+    ): PreflightResult {
+        if ($requiredLeads <= 0) {
+            return new PreflightResult(true, 0, 0, 0);
+        }
+
+        $capacity = (int) $this->converter->convert($balanceRub, $deliveredInMonth, $tiers)['leads'];
+        $passes = $capacity >= $requiredLeads;
+
+        return new PreflightResult(
+            passes: $passes,
+            requiredLeads: $requiredLeads,
+            capacityLeads: $capacity,
+            deficitLeads: $passes ? 0 : ($requiredLeads - $capacity),
+        );
+    }
+}
diff --git a/app/app/Services/Billing/PreflightResult.php b/app/app/Services/Billing/PreflightResult.php
new file mode 100644
index 00000000..eb99899e
--- /dev/null
+++ b/app/app/Services/Billing/PreflightResult.php
@@ -0,0 +1,20 @@
+<?php
+
+declare(strict_types=1);
+
+namespace App\Services\Billing;
+
+/**
+ * Результат преfflight-проверки платёжеспособности тенанта (Billing v2 Spec C).
+ *
+ * Spec: docs/superpowers/specs/2026-05-24-billing-v2-spec-c-preflight-vtb-design.md §3.3
+ */
+final class PreflightResult
+{
+    public function __construct(
+        public readonly bool $passes,
+        public readonly int $requiredLeads,
+        public readonly int $capacityLeads,
+        public readonly int $deficitLeads,
+    ) {}
+}
diff --git a/app/tests/Unit/Billing/BalancePreflightServiceTest.php b/app/tests/Unit/Billing/BalancePreflightServiceTest.php
new file mode 100644
index 00000000..e08b8c39
--- /dev/null
+++ b/app/tests/Unit/Billing/BalancePreflightServiceTest.php
@@ -0,0 +1,52 @@
+<?php
+
+declare(strict_types=1);
+
+use App\Models\PricingTier;
+use App\Services\Billing\BalancePreflightService;
+use Illuminate\Database\Eloquent\Collection;
+
+function makeTiers(): Collection
+{
+    // 1 ступень: цена 50₽/лид (5000 копеек), безлимитная.
+    return new Collection([
+        new PricingTier(['tier_no' => 1, 'leads_in_tier' => null, 'price_per_lead_kopecks' => 5000, 'is_active' => true]),
+    ]);
+}
+
+it('passes when balance covers full daily limit', function () {
+    $service = new BalancePreflightService;
+    // 2000₽ / 50₽ = 40 лидов capacity; нужно 30 → проходит.
+    $result = $service->evaluate(
+        balanceRub: '2000.00',
+        deliveredInMonth: 0,
+        requiredLeads: 30,
+        tiers: makeTiers(),
+    );
+
+    expect($result->passes)->toBeTrue();
+    expect($result->capacityLeads)->toBe(40);
+    expect($result->requiredLeads)->toBe(30);
+    expect($result->deficitLeads)->toBe(0);
+});
+
+it('fails when balance below full daily limit', function () {
+    $service = new BalancePreflightService;
+    // 1000₽ / 50₽ = 20 лидов capacity; нужно 30 → не проходит, дефицит 10.
+    $result = $service->evaluate(
+        balanceRub: '1000.00',
+        deliveredInMonth: 0,
+        requiredLeads: 30,
+        tiers: makeTiers(),
+    );
+
+    expect($result->passes)->toBeFalse();
+    expect($result->capacityLeads)->toBe(20);
+    expect($result->deficitLeads)->toBe(10);
+});
+
+it('passes trivially when requiredLeads is zero', function () {
+    $service = new BalancePreflightService;
+    $result = $service->evaluate('0.00', 0, 0, makeTiers());
+    expect($result->passes)->toBeTrue();
+});