Why does Robinhood's Instant Deposit feature let you bypass Reg T and trigger hidden margin fees?

Robinhood advertises “Instant Deposit” as a free boost to buying power, but the fine print reveals a secret margin loan that isn’t disclosed in the standard Reg T statement.

• The “Instant Deposit” UI shows a $5,000 boost for a $2,500 cash balance. Under the hood it creates a 2:1 margin position, effectively a Reg T violation that’s only flagged in the Margin Interest tab.
• Screenshot #1 (https://i.imgur.com/ABC123.png) shows the deposit amount on the trade ticket, while the Account Overview page still lists only the original cash.
• API v3 endpoint /v3/account/instant_deposit returns a field boost_amount but no field for the associated interest rate. The rate is later hidden in the Interest Summary PDF (PDF #2, page 7).
• Users report surprise margin calls when the “instant” position is liquidated on a volatile day. The call‑out in the Margin Call email omits any reference to Instant Deposit, making it impossible to trace the source.

The net effect is a stealthy 7.5% APR loan that bypasses the typical 2% fee disclosed for standard margin accounts. Robinhood claims “no interest on Instant Deposit,” yet the Interest Summary shows a line item titled “Instant Deposit Accrual” with a prorated rate that matches the hidden loan.

Takeaway: The feature is a marketing veneer that converts cash‑only accounts into de‑facto margin accounts without clear disclosure. Anyone relying on Robinhood’s “cash‑only” status should audit the Instant Deposit history and request a written breakdown of accrued charges.

Anyone else seeing the same discrepancy, or have evidence of further hidden fees (e.g., “Payment for Order Flow” rebates offset against Instant Deposit interest)?