diff --git a/src/food-market.api/Controllers/DocumentsController.cs b/src/food-market.api/Controllers/DocumentsController.cs
new file mode 100644
index 0000000..391d959
--- /dev/null
+++ b/src/food-market.api/Controllers/DocumentsController.cs
@@ -0,0 +1,100 @@
+using foodmarket.Application.Common.Tenancy;
+using foodmarket.Infrastructure.Persistence;
+using Microsoft.AspNetCore.Authorization;
+using Microsoft.AspNetCore.Mvc;
+using Microsoft.EntityFrameworkCore;
+
+namespace foodmarket.Api.Controllers;
+
+/// <summary>Сквозные связи документов (как «Связанные документы» в МойСкладе):
+/// по типу+id документа возвращает «основание» (на основании чего создан) и
+/// «связанные» (что создано на основании этого / оплаты / возвраты). Единый
+/// источник для блока «Связанные документы» на всех страницах документов.</summary>
+[ApiController]
+[Authorize]
+[Route("api/documents")]
+public class DocumentsController : ControllerBase
+{
+    private readonly AppDbContext _db;
+    public DocumentsController(AppDbContext db) => _db = db;
+
+    public record DocRef(string type, Guid id, string number, DateTime date, string? relation);
+    public record RelatedResult(IReadOnlyList<DocRef> basedOn, IReadOnlyList<DocRef> related);
+
+    /// <summary>type ∈ supply | supplier-return | retail-sale | inventory | enter | loss.</summary>
+    [HttpGet("{type}/{id:guid}/related")]
+    public async Task<ActionResult<RelatedResult>> Related(string type, Guid id, CancellationToken ct)
+    {
+        var basedOn = new List<DocRef>();
+        var related = new List<DocRef>();
+
+        switch (type)
+        {
+            case "supply":
+            {
+                // На основании этой приёмки: возвраты поставщику + оплаты.
+                related.AddRange(await _db.SupplierReturns.AsNoTracking()
+                    .Where(r => r.ReferenceSupplyId == id)
+                    .Select(r => new DocRef("supplier-return", r.Id, r.Number, r.Date, "возврат поставщику")).ToListAsync(ct));
+                related.AddRange(await _db.MoneyTransactions.AsNoTracking()
+                    .Where(t => t.Links.Any(l => l.SupplyId == id))
+                    .Select(t => new DocRef("money", t.Id, t.Number, t.Date, "оплата")).ToListAsync(ct));
+                break;
+            }
+            case "supplier-return":
+            {
+                var refSupplyId = await _db.SupplierReturns.AsNoTracking().Where(r => r.Id == id)
+                    .Select(r => r.ReferenceSupplyId).FirstOrDefaultAsync(ct);
+                if (refSupplyId is { } rs)
+                    basedOn.AddRange(await _db.Supplies.AsNoTracking().Where(s => s.Id == rs)
+                        .Select(s => new DocRef("supply", s.Id, s.Number, s.Date, "приёмка")).ToListAsync(ct));
+                related.AddRange(await _db.MoneyTransactions.AsNoTracking()
+                    .Where(t => t.Links.Any(l => l.SupplierReturnId == id))
+                    .Select(t => new DocRef("money", t.Id, t.Number, t.Date, "возврат денег")).ToListAsync(ct));
+                break;
+            }
+            case "retail-sale":
+            {
+                var refSaleId = await _db.RetailSales.AsNoTracking().Where(s => s.Id == id)
+                    .Select(s => s.ReferenceSaleId).FirstOrDefaultAsync(ct);
+                if (refSaleId is { } rsi)
+                    basedOn.AddRange(await _db.RetailSales.AsNoTracking().Where(s => s.Id == rsi)
+                        .Select(s => new DocRef("retail-sale", s.Id, s.Number, s.Date, "чек")).ToListAsync(ct));
+                related.AddRange(await _db.RetailSales.AsNoTracking()
+                    .Where(s => s.ReferenceSaleId == id)
+                    .Select(s => new DocRef("retail-sale", s.Id, s.Number, s.Date, "возврат")).ToListAsync(ct));
+                break;
+            }
+            case "inventory":
+            {
+                related.AddRange(await _db.Enters.AsNoTracking().Where(e => e.InventoryDocId == id)
+                    .Select(e => new DocRef("enter", e.Id, e.Number, e.Date, "оприходование")).ToListAsync(ct));
+                related.AddRange(await _db.Losses.AsNoTracking().Where(l => l.InventoryDocId == id)
+                    .Select(l => new DocRef("loss", l.Id, l.Number, l.Date, "списание")).ToListAsync(ct));
+                break;
+            }
+            case "enter":
+            {
+                var invId = await _db.Enters.AsNoTracking().Where(e => e.Id == id).Select(e => e.InventoryDocId).FirstOrDefaultAsync(ct);
+                if (invId is { } iv)
+                    basedOn.AddRange(await _db.InventoryDocs.AsNoTracking().Where(x => x.Id == iv)
+                        .Select(x => new DocRef("inventory", x.Id, x.Number, x.Date, "инвентаризация")).ToListAsync(ct));
+                break;
+            }
+            case "loss":
+            {
+                var invId = await _db.Losses.AsNoTracking().Where(l => l.Id == id).Select(l => l.InventoryDocId).FirstOrDefaultAsync(ct);
+                if (invId is { } iv)
+                    basedOn.AddRange(await _db.InventoryDocs.AsNoTracking().Where(x => x.Id == iv)
+                        .Select(x => new DocRef("inventory", x.Id, x.Number, x.Date, "инвентаризация")).ToListAsync(ct));
+                break;
+            }
+            default:
+                return BadRequest(new { error = $"Неизвестный тип документа «{type}»." });
+        }
+
+        return new RelatedResult(
+            basedOn.OrderBy(x => x.date).ToList(),
+            related.OrderBy(x => x.date).ToList());
+    }
+}
diff --git a/src/food-market.web/src/components/RelatedDocsBlock.tsx b/src/food-market.web/src/components/RelatedDocsBlock.tsx
new file mode 100644
index 0000000..2c88520
--- /dev/null
+++ b/src/food-market.web/src/components/RelatedDocsBlock.tsx
@@ -0,0 +1,61 @@
+import { useQuery } from '@tanstack/react-query'
+import { Link } from 'react-router-dom'
+import { LinkIcon } from 'lucide-react'
+import { api } from '@/lib/api'
+
+export type DocType = 'supply' | 'supplier-return' | 'retail-sale' | 'inventory' | 'enter' | 'loss'
+
+interface DocRef { type: string; id: string; number: string; date: string; relation: string | null }
+interface Related { basedOn: DocRef[]; related: DocRef[] }
+
+const PATH: Record<string, (id: string) => string | null> = {
+  'supply': (id) => `/purchases/supplies/${id}`,
+  'supplier-return': (id) => `/purchases/supplier-returns/${id}`,
+  'retail-sale': (id) => `/sales/retail/${id}`,
+  'inventory': (id) => `/inventory/inventories/${id}`,
+  'enter': (id) => `/inventory/enters/${id}`,
+  'loss': (id) => `/inventory/losses/${id}`,
+  'money': () => `/money/transactions`,
+}
+
+function Row({ d }: { d: DocRef }) {
+  const to = PATH[d.type]?.(d.id)
+  const label = <>{d.relation ? <span className="text-slate-400">{d.relation}: </span> : null}<span className="font-mono">{d.number}</span> <span className="text-slate-400 text-xs">{new Date(d.date).toLocaleDateString('ru')}</span></>
+  return (
+    <li className="py-0.5 text-sm">
+      {to ? <Link to={to} className="text-blue-600 dark:text-blue-400 hover:underline">{label}</Link> : <span>{label}</span>}
+    </li>
+  )
+}
+
+/**
+ * Блок «Связанные документы» и «На основании …» — как в инвентаризации, единый
+ * для всех документов (п.5 паритета). Скрывается, если связей нет.
+ */
+export function RelatedDocsBlock({ type, id }: { type: DocType; id?: string }) {
+  const { data } = useQuery<Related>({
+    queryKey: ['/api/documents/related', type, id],
+    queryFn: async () => (await api.get<Related>(`/api/documents/${type}/${id}/related`)).data,
+    enabled: !!id,
+  })
+  if (!data || (data.basedOn.length === 0 && data.related.length === 0)) return null
+  return (
+    <div className="bg-white dark:bg-slate-900 rounded-xl border border-slate-200 dark:border-slate-800 p-4">
+      <div className="flex items-center gap-2 text-xs font-semibold uppercase tracking-wide text-slate-500 dark:text-slate-400 mb-2">
+        <LinkIcon className="w-3.5 h-3.5" /> Связанные документы
+      </div>
+      {data.basedOn.length > 0 && (
+        <div className="mb-2">
+          <div className="text-xs text-slate-400 mb-0.5">На основании</div>
+          <ul>{data.basedOn.map((d) => <Row key={d.id} d={d} />)}</ul>
+        </div>
+      )}
+      {data.related.length > 0 && (
+        <div>
+          <div className="text-xs text-slate-400 mb-0.5">Создано на основании этого</div>
+          <ul>{data.related.map((d) => <Row key={d.id} d={d} />)}</ul>
+        </div>
+      )}
+    </div>
+  )
+}
diff --git a/src/food-market.web/src/pages/EnterEditPage.tsx b/src/food-market.web/src/pages/EnterEditPage.tsx
index 8ecaa6d..8b41f1b 100644
--- a/src/food-market.web/src/pages/EnterEditPage.tsx
+++ b/src/food-market.web/src/pages/EnterEditPage.tsx
@@ -1,4 +1,5 @@
 import { useState, useEffect, type FormEvent } from 'react'
+import { RelatedDocsBlock } from '@/components/RelatedDocsBlock'
 import { useNavigate, useParams, Link } from 'react-router-dom'
 import { useQuery, useQueryClient, useMutation } from '@tanstack/react-query'
 import { ArrowLeft, Plus, Trash2, Save, CheckCircle } from 'lucide-react'
@@ -255,6 +256,7 @@ export function EnterEditPage() {
 
       <div className="flex-1 overflow-auto">
         <div className="max-w-5xl mx-auto p-3 sm:p-6 space-y-4">
+          {!isNew && id && <RelatedDocsBlock type="enter" id={id} />}
           {error && (
             <div className="p-3 rounded-md bg-red-50 text-red-700 text-sm border border-red-200">{error}</div>
           )}
diff --git a/src/food-market.web/src/pages/LossEditPage.tsx b/src/food-market.web/src/pages/LossEditPage.tsx
index de2b8f6..fbd311f 100644
--- a/src/food-market.web/src/pages/LossEditPage.tsx
+++ b/src/food-market.web/src/pages/LossEditPage.tsx
@@ -1,4 +1,5 @@
 import { useState, useEffect, type FormEvent } from 'react'
+import { RelatedDocsBlock } from '@/components/RelatedDocsBlock'
 import { useNavigate, useParams, Link } from 'react-router-dom'
 import { useQuery, useQueryClient, useMutation } from '@tanstack/react-query'
 import { ArrowLeft, Plus, Trash2, Save, CheckCircle } from 'lucide-react'
@@ -258,6 +259,7 @@ export function LossEditPage() {
 
       <div className="flex-1 overflow-auto">
         <div className="max-w-5xl mx-auto p-3 sm:p-6 space-y-4">
+          {!isNew && id && <RelatedDocsBlock type="loss" id={id} />}
           {error && (
             <div className="p-3 rounded-md bg-red-50 text-red-700 text-sm border border-red-200">{error}</div>
           )}
diff --git a/src/food-market.web/src/pages/RetailSaleEditPage.tsx b/src/food-market.web/src/pages/RetailSaleEditPage.tsx
index 66b7b0a..f428023 100644
--- a/src/food-market.web/src/pages/RetailSaleEditPage.tsx
+++ b/src/food-market.web/src/pages/RetailSaleEditPage.tsx
@@ -1,4 +1,5 @@
 import { useState, useEffect, type FormEvent, type ReactNode } from 'react'
+import { RelatedDocsBlock } from '@/components/RelatedDocsBlock'
 import { useNavigate, useParams, Link } from 'react-router-dom'
 import { useQuery, useQueryClient, useMutation } from '@tanstack/react-query'
 import { ArrowLeft, Plus, Trash2, Save, CheckCircle, Undo2 } from 'lucide-react'
@@ -301,6 +302,7 @@ export function RetailSaleEditPage() {
       <div className="flex-1 overflow-auto">
         <div className="max-w-6xl mx-auto p-3 sm:p-6 space-y-4 sm:space-y-5">
           {error && <div className="p-3 rounded-md bg-red-50 text-red-700 text-sm border border-red-200">{error}</div>}
+          {!isNew && id && <RelatedDocsBlock type="retail-sale" id={id} />}
 
           <Section title="Реквизиты чека">
             <div className="grid grid-cols-1 md:grid-cols-3 gap-x-4 gap-y-3">
diff --git a/src/food-market.web/src/pages/SupplierReturnEditPage.tsx b/src/food-market.web/src/pages/SupplierReturnEditPage.tsx
index 4f3c1e6..c6cb280 100644
--- a/src/food-market.web/src/pages/SupplierReturnEditPage.tsx
+++ b/src/food-market.web/src/pages/SupplierReturnEditPage.tsx
@@ -1,4 +1,5 @@
 import { useState, useEffect, type FormEvent } from 'react'
+import { RelatedDocsBlock } from '@/components/RelatedDocsBlock'
 import { useNavigate, useParams, Link } from 'react-router-dom'
 import { useQuery, useQueryClient, useMutation } from '@tanstack/react-query'
 import { ArrowLeft, Plus, Trash2, Save, CheckCircle } from 'lucide-react'
@@ -253,6 +254,7 @@ export function SupplierReturnEditPage() {
 
       <div className="flex-1 overflow-auto">
         <div className="max-w-5xl mx-auto p-3 sm:p-6 space-y-4">
+          {!isNew && id && <RelatedDocsBlock type="supplier-return" id={id} />}
           {error && (
             <div className="p-3 rounded-md bg-red-50 text-red-700 text-sm border border-red-200">{error}</div>
           )}
diff --git a/src/food-market.web/src/pages/SupplyEditPage.tsx b/src/food-market.web/src/pages/SupplyEditPage.tsx
index e44cfbf..cdce480 100644
--- a/src/food-market.web/src/pages/SupplyEditPage.tsx
+++ b/src/food-market.web/src/pages/SupplyEditPage.tsx
@@ -1,4 +1,5 @@
 import { useState, useEffect, useRef, type FormEvent, type ReactNode } from 'react'
+import { RelatedDocsBlock } from '@/components/RelatedDocsBlock'
 import { useNavigate, useParams, Link } from 'react-router-dom'
 import { useQuery, useQueryClient, useMutation } from '@tanstack/react-query'
 import { ArrowLeft, Plus, Trash2, Save, CheckCircle, Undo2 } from 'lucide-react'
@@ -350,6 +351,7 @@ export function SupplyEditPage() {
       {/* Scrollable body */}
       <div ref={scrollBodyRef} className="flex-1 overflow-auto">
         <div className="max-w-6xl mx-auto p-3 sm:p-6 space-y-4 sm:space-y-5">
+          {!isNew && id && <RelatedDocsBlock type="supply" id={id} />}
           {error && (
             <div className="p-3 rounded-md bg-red-50 text-red-700 text-sm border border-red-200">{error}</div>
           )}
diff --git a/tests/food-market.IntegrationTests/SupplierReturnFromSupplyTests.cs b/tests/food-market.IntegrationTests/SupplierReturnFromSupplyTests.cs
index e6f75f2..854db55 100644
--- a/tests/food-market.IntegrationTests/SupplierReturnFromSupplyTests.cs
+++ b/tests/food-market.IntegrationTests/SupplierReturnFromSupplyTests.cs
@@ -38,5 +38,14 @@ public async Task CreateFromSupply_presets_lines_and_links_supply()
         lines.Should().ContainSingle(l => l.GetProperty("productId").GetString() == product);
         lines.First().GetProperty("quantity").GetDecimal().Should().Be(10m);
         lines.First().GetProperty("unitPrice").GetDecimal().Should().Be(100m);
+        var returnId = r.GetProperty("id").GetString();
+
+        // Связи документов (п.5): приёмка видит возврат как связанный; возврат — приёмку как основание.
+        var supRel = await api.GetJsonAsync($"/api/documents/supply/{supplyId}/related");
+        supRel.GetProperty("related").EnumerateArray()
+            .Should().Contain(x => x.GetProperty("type").GetString() == "supplier-return" && x.GetProperty("id").GetString() == returnId);
+        var retRel = await api.GetJsonAsync($"/api/documents/supplier-return/{returnId}/related");
+        retRel.GetProperty("basedOn").EnumerateArray()
+            .Should().Contain(x => x.GetProperty("type").GetString() == "supply" && x.GetProperty("id").GetString() == supplyId);
     }
 }