diff --git a/docs/shared-expenses-design.md b/docs/shared-expenses-design.md
index ec0c09a..9dd9ad9 100644
--- a/docs/shared-expenses-design.md
+++ b/docs/shared-expenses-design.md
@@ -203,15 +203,7 @@ fortnight of principal into spend, the error migration 0014 exists to prevent.
    marks Molina's money in all six known cases, but it is a description match on
    a free-text field. Acceptable as a *suggestion* requiring confirmation, not
    as an automatic rule.
-3. **Two unattributable Sonu payments.** #3 ($3,779.33, 12 Apr) and #8
-   ($4,794.06, 16 May) are narrated only as "transfer", and payments are made
-   grouped — one transfer can cover a trip and the household tab together. That
-   is already expressible: `split_payments` has no unique constraint on
-   `linked_transaction_id`, so one bank transfer can carry several rows, each
-   with its own `trip_id`. What is missing is the breakdown. Both currently sit
-   whole on the household tab; splitting them moves money between tabs without
-   changing her overall balance.
-4. **The solo leg.** A Qantas booking on 23 Apr (txn 2849, $1,366.40) is the
+3. **The solo leg.** A Qantas booking on 23 Apr (txn 2849, $1,366.40) is the
    flight to Bangkok that begins a solo leg, and the Singapore spending
    ($2,242.05, 40 rows, to 9 May) is solo — not shared. It has no trip record.
    Worth one if trip *cost* is wanted for it; nothing about sharing depends on
@@ -224,3 +216,23 @@ fortnight of principal into spend, the error migration 0014 exists to prevent.
   invisible to trip analytics. Includes one advance booking on 17 Mar
   (Ticketmaster Nanterre) and the 12 Apr handover-day rows, which were already
   held out of Europe 2026.
+
+- **Grouped payments, split by scope.** Payments are made grouped — one transfer
+  covers several tabs — and that needs no schema change, because
+  `split_payments` has no unique constraint on `linked_transaction_id`. So one
+  bank transfer carries one row per scope, and the rows re-add to the transfer.
+
+  Sonu's two "transfer" payments were allocated Europe-first, remainder to
+  household, chronologically so each settles what was outstanding when it was
+  made:
+
+  | Transfer | Scope | Amount |
+  |---|---|---:|
+  | $3,779.33, 12 Apr (txn 4111) | Europe 2026 | 1,084.61 |
+  | | Europe — Sonu + Sunny | 2,694.72 |
+  | $4,794.06, 16 May (txn 4121) | Europe — Sonu + Sunny | 1,145.52 |
+  | | household | 3,648.54 |
+
+  Both Europe tabs now read $0.00 and her overall balance is unchanged at
+  $5,428.08 — allocation moves money between tabs, never between people. That
+  invariance is the check worth repeating on any future re-allocation.