Frame 1 — Broker books are live
House · T-2 08:00 ET
The broker's general ledger comes online before the customer ever shows up. Empty slate, no positions, no obligations. Just a GL and a securities master ready to receive entries. This is the broker's authoritative book — but as we'll see, it's only one of three ledgers that matter.

Frame 2 — DTC inventory
House · T-2 09:00 ET
The broker's securities position isn't really at the broker — it's at DTC, immobilized in book-entry form. ACME and ZNTH each show 5,000 shares in the broker's DTC participant file. The broker books a mirror entry on its own GL: Sec @ DTC on the asset side, Cust Sec obligation on the liability side. The DTC record is the master; the broker's book is a copy that has to be reconciled.

Frame 3 — Fedwire credit advice
House · T-1 10:00 ET
House liquidity arrives via Fedwire — $1,000,000 lands in the broker's Fed account. Cash sits at the Fed, securities sit at DTC. Two separate ledgers, two separate settlement systems, one general ledger trying to reflect both.

Frame 4 — Open Jane's account
Jane · T-1 14:00 ET
Standard customer onboarding. Margin account, Reg-T governed, hypothecation enabled. Status flagged PENDG_FUNDING because no money has arrived yet. The account exists on the broker's books but not really anywhere else.

Frame 5 — ACH funding
Jane · T-1 14:30 → T 09:00 ET
Jane initiates a $10,000 ACH transfer from her bank. Two beats: first the cash shows up [PENDG T+1] because ACH settles next banking day. The broker's GL records the entry with a pending status pill. Next morning, the second beat — the pill flips to settled. Even funding the account isn't instantaneous.

Frame 6 — Margin loan extended
Jane · T 09:30 ET
Broker extends a $10,000 margin loan against Jane's $10,000 cash. Reg-T 50% complies. Her cash balance now reads $20,000, with a $10,000 margin loan on the credit side. But this only exists on the broker's GL. NSCC and DTC have no idea. The broker is on the hook for the loan; the rest of the world doesn't see it.

Frame 7 — Buy 100 ACME @ $100
Jane · T 10:02 ET
FIX execution report from the venue. Trade-date entry on the broker's books — both the NSCC-side leg [T+1 PENDG] and the customer-side internal allocation [internal, immediate]. Jane sees ACME shares in her account now, but the actual securities won't move at NSCC until tomorrow.

Frame 8 — ACME closes at $130
Jane · T 16:00 ET
Mark-to-market at the close. ACME jumped to $130. Broker books a $3,000 unrealized P&L on Jane's account — internal accounting only. Her securities position still shows PENDG T+1 because the underlying NSCC obligation hasn't settled. MTM is real in one sense (P&L tracks); not real in another (the shares aren't really "hers" yet).

Frame 9 — Sell 100 ACME @ $130
Jane · T+1 09:45 ET
Jane sells next morning. Two simultaneous things happen on the broker's books:
1. Yesterday's BUY settles via NSCC CNS net — [SETTLED, buy from T]
2. Today's SELL is booked [T+1 PENDG, sell] — won't settle until T+2
Two beats: first her position reads "ACME holding settled, ready to sell"; second beat, the sell posts and her cash spikes to $23,000 with the new pending line. The book is always a day mismatched. $3,000 of unrealized P&L crystallizes as realized.

Frame 10 — Buy 150 ZNTH @ $125
Jane · T+1 10:30 ET
Jane redeploys $18,750 into ZNTH at $125. T+2 settlement. She's now leveraged — using $20K of buying power against $10K of equity. The broker's GL reflects the new position immediately; NSCC won't see it until tomorrow's net.

Frame 11 — ZNTH crashes to $50, MARGIN CALL
Jane · T+1 14:00 ET
ZNTH cratters to $50 intraday. Position market value: $7,500. Account equity: $1,750 (23%). Maintenance requirement: 25%. The risk system fires a margin call in real time. But the cash to cure cannot move intraday — even Jane's own residual $4,250 is locked in SETTLED (internal) mode pending the T+2 NSCC settlement of the ZNTH buy. The broker books an $11,250 unrealized loss against ZNTH.

Frame 12 — Internal cash sweep against loan
Jane · T+1 14:15 ET
The broker sweeps Jane's $4,250 free credit against the margin loan. Loan drops to $5,750. But this is only on the broker's books. NSCC and DTC don't see it. It doesn't actually cure the call — equity is still below maintenance. Internal accounting fix only.

Frame 13 — Forced liquidation: 10 ZNTH @ $50
Jane · T+1 14:25 ET
House cures the call by liquidating 10 ZNTH shares at $50. $500 in cash recovered, used to pay down the margin loan to $5,250. Realized loss of $750. The street settlement is two days out — NSCC won't actually move the cash and shares until T+2. The broker has cured the call on its books while still carrying T+2-pending NSCC obligations.

Frame 14 — Account close: sell 130, keep 10 for delivery
Jane · T+1 15:30 ET
Jane elects to close the account. Sells 130 ZNTH at $50, keeps the remaining 10 for physical delivery to her DTC street name. Her broker GL now shows $1,250 cash, $500 in ZNTH (10 shares awaiting delivery), zero margin loan. P&L crystallized: realized -$7,500, unrealized -$750. NSCC still owes the broker cash for two days. Customer is "flat" on the broker's books; the broker is carrying multiple pending lines on her behalf.

Frame 15 — NSCC nets the broker's pending lines
House · T+2 09:00 ET
Two days after the call, the back office finally catches up. NSCC CNS net settlement runs and clears all the accumulated pending lines: net cash +$1,250, net ZNTH -10 sh (transferred to customer street). Broker GL is now reconciled to NSCC. The "books are real" — finally.

Frame 16 — DTC re-registers 10 ZNTH to Jane
Jane · T+2 09:15 ET
Round-trip on the DTC channel — up arrow first (broker instructs DTC), down arrow second (DTC confirms position transfer). 10 ZNTH shares move from broker street to Jane's own DTC street name. The redemption is real: shares left the broker's universe and now sit in her name at the central depository. Her ZNTH line on the broker's GL drops to $0. Her cash still pending the ACH out — [PENDG T+3 (ACH out)].

Frame 17 — Broker initiates ACH out for $1,250
House · T+2 10:00 ET
Broker fires the ACH instruction to send Jane's residual $1,250 to her bank. Cash @ Fed reduces from $1,000,000 to $998,750. Status: pending — the ACH won't land until next banking day.

Frame 18 — $1,250 lands in Jane's bank, account fully closed
Jane · T+3 morning
ACH settlement confirmation arrives. Jane's bank receives the $1,250. Account ACCT-7841 status: CLOSED. Final state on the broker's books: zero cash, zero securities, zero loan, zero capital. Realized P&L of -$7,500 and unrealized residual of -$750 remain as the historical accounting trail.