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The Closed Loop / The rail
Opening a rail

A rail opens when a deposit on it settles, and not before

A rail is not a payment method on file. It is a payment method that has carried a completed deposit. The gap between those two things explains a specific and common failure: the withdrawal names a destination the reader has used for years, and the operator says the rail does not exist.

Rail stub
Opens on
a settled deposit
Settlement, not authorisation
the rail’s own clock
Saved but unused
cap of 0.00
Order
published; oldest first on the sample
the railA payment method that has carried a completed deposit - not a method saved on the account
the capWhat a rail paid in, less what it has already returned, and never below zero
released moneyThe part of a balance above every cap: payable, and travelling by the operator’s own route
Direct answerA rail may carry a withdrawal only after a deposit on that exact rail has completed. A card saved to the account, a bank account the reader uses weekly elsewhere, and an address typed once all have a cap of zero until a deposit settles on them. A saved method is a convenience, not a rail.

Authorised, settled, and the difference

A deposit passes through stages, and only the last one opens the rail. The stage a reader sees - the balance rising - is not the stage that matters, which is why an operator can correctly say that a deposit which has already appeared in the balance has not yet opened anything.

  1. Requested. The payment is authorised against the rail. The balance may already show it, because operators credit on authorisation to keep the product usable.
  2. Authorised. The rail’s issuer has approved the amount. It can still be reversed, and at this stage the operator has the money on a promise rather than in hand.
  3. Settled. The rail has moved the money and the operator can no longer lose it to a failed authorisation. The cap is created here, which is why a deposit made minutes ago often does not unlock a withdrawal made in the same session.
  4. Reversed. The other ending. A failed authorisation, a chargeback or a recalled transfer removes the deposit again - and takes the cap with it, because a rail can only have returned what it actually paid in.
What a test deposit actually buys, worked on S3rail state before never used cap = 0.00 test deposit 10.00, settles in 1 working day cap created 10.00 - 0.00 = 10.00 requested = 400.00 amount that can use the new rail 400.00 - 390.00 = 10.00 share of the request 10.00 / 400.00 = 2.5% result 390.00 still has to travel on the rails that paid it

This is the single most misread number on the desk. A 10.00 test deposit unlocks 10.00, not the rail’s future capacity: it creates a cap equal to its own amount, and the 400.00 request still needs rails that took in 390.00 between them. The test deposit is worth doing for a different reason - it proves the destination and the name before a large payment is attempted on it - and it is not a way of moving a large sum to a rail the operator has never seen money from.

Which rail is tried first

Once several rails are open, the order they are paid in is a published choice, and the three common ones behave differently.

Oldest first

The rail that paid earliest is paid first and its cap closes soonest. This is the sample’s default. It has the quiet effect of retiring old rails: after a year of withdrawals, the rail used at sign-up is spent and no longer part of the picture.

Newest first

The most recent deposit is returned first. This suits a reader who wants a specific recent rail cleared, and it has a real consequence: the rail likely to be closed is the one most recently used, which is usually the one still in working order.

Largest cap first

Rails are ordered by how much they can return, so the request is met by the fewest payments. It usually gives the smallest number of separate payments and is the order that most reduces the split.

None of the three is more correct than the others, and the operator is free to change it - the order is a policy line in a withdrawal section, not a term the account holder agreed to individually. What matters for a reader is that the order decides which rail is retired, and a rail that has gone cannot be retired at all: it keeps its cap indefinitely, and the cap keeps being skipped.

Opening a rail deliberately

If the plan is to withdraw to a specific destination, the way to make that destination a rail is to deposit from it once and let the deposit settle. Two practical points follow, and both are about timing rather than amount.

Do it before the withdrawal, not during

A deposit made in the same session as the request usually has not settled, so the rail is not open when the request is assessed. The gap is one to three working days for most rails, and the whole point of doing it deliberately is to spend that gap once rather than twice.

Deposit enough to matter, or accept the cap

The cap equals the deposit. A rail opened with 10.00 can return 10.00. A reader who wants a destination to be able to carry a real payment has to have sent a real payment through it, which for some people is the entire point of the mechanism.