OTC or exchange: what changes when the order gets large

Most advice about selling cryptocurrency assumes an amount where the answer does not matter. Below some size, any reasonable venue gives you roughly the same outcome and the sensible choice is whichever is easiest.

Above that size the venue stops being a detail and becomes the largest single variable in what you receive. This guide explains the mechanism behind that, where the crossover tends to fall, and what to ask before committing to either route.

What an order book actually does with your order

An exchange order book is a list of bids: someone will buy 0.4 BTC at one price, someone else 1.2 BTC slightly lower, someone else more, lower still. The price you see quoted is the best bid at that instant, for whatever quantity happens to sit there.

A market sell order fills against those bids in order. It takes the best one, exhausts it, takes the next, and continues until your order is complete. Your average price is the weighted average of everything it consumed, not the number displayed when you pressed the button.

That gap between the price shown and the price achieved is slippage, and it has two properties worth understanding.

It is not linear. Doubling your order does not double the cost. Depth thins as you move away from the touch, so each additional unit tends to fill worse than the one before.

It is not visible in advance from a chart. Price history shows where trades happened, not how much size was available at each level. Two assets showing identical charts can absorb very different volumes before the price moves.

Three costs people conflate

Comparing venues is difficult mostly because the costs have different names in different places and only some of them are advertised.

Spread is the gap between the best bid and the best ask. You pay half of it on entry and half on exit, and it exists whether or not anyone calls it a fee.

Commission is the explicit percentage a venue charges. It is the number people compare, and it is usually the smallest of the three on a large order.

Slippage is what your own order does to the price while it fills. On a small order it rounds to nothing. On a large one it can exceed the commission by a wide margin.

A venue advertising the lowest commission can easily deliver the worst outcome on size, because the number being advertised is the one that matters least. The only comparison that means anything is the total amount that arrives in your account.

Market impact, and why it does not come back

Beyond your own fill there is a second effect. A large sale visibly consumes bids, and other participants see it happen. Some withdraw quotes, some trade ahead of what they expect to follow. The book that reprices around your order is not obliged to reprice back afterwards.

This is why splitting a large order into smaller pieces helps less than people expect. It reduces the impact of any single fill, and it extends the time you are exposed to the market while your intention becomes readable. On a genuinely large order you are choosing between a known cost now and an unknown cost spread over hours.

How an OTC quote is built

An OTC desk does not put your order in a book. It quotes a single price for the entire amount, and you accept it or you do not.

The price is not charity. The desk is taking the position from you and will hedge it, and the spread it quotes covers the cost of doing that plus its margin. What you are buying is the transfer of execution risk: the desk absorbs whatever it costs to unwind, and you receive the number you agreed.

That produces two differences that matter more than the headline rate.

The outcome is known before you commit. You are comparing a firm number against your own alternative, not discovering an average afterwards.

Your order does not move a public market. Nothing is broadcast into a book, so nothing reprices in response to what you are doing.

The trade-off is real and worth stating plainly: you give up the possibility of a better fill. If the book would have absorbed your order without complaint, an OTC quote will usually cost slightly more than a well-executed exchange sale. You are paying for certainty, and certainty is only worth buying when the uncertainty is material.

Where the crossover sits

There is no universal threshold, and anyone quoting one is guessing. What determines it:

• Liquidity of the specific asset. Major assets absorb far more than smaller ones. The same amount can be trivial in one market and disruptive in another.
• Depth at the moment you trade, which varies by time of day and by whatever else is happening in the market.
• How the venue's book is composed. Two exchanges with similar volume can have very different depth near the touch.
• Your urgency. Patience is what buys a better exchange fill, and a deadline removes it.

The practical test is not a number but a comparison. Ask an OTC desk for an indicative quote on the amount you actually hold. Then look at the order book on the venue you would otherwise use and estimate what your order would consume. If the book absorbs it in the top few levels, the exchange is probably fine. If your order would visibly clear several levels, you have your answer.

Getting an indicative quote costs nothing and commits you to nothing. Not getting one is how people discover slippage after the fact.

What to ask a desk before trading

• Is the quote firm, and for how long? A price that moves between agreement and execution is not a quote.
• Is it all-in? Spread, commission and network fees should resolve to one number: what arrives.
• What is the minimum? Desks have floors, and below them the exchange route is the right one.
• Where does settlement go? To a verified account in your own name, or to third parties. This affects what documents you will need and how your bank reacts. See how to convert cryptocurrency to a bank account.
• What is required before trading? Verification and source-of-funds evidence come first at any regulated desk. See source of funds.
• Which registrations does the desk hold? Registration is not endorsement or a guarantee of anything, but its absence is meaningful.

When the exchange is the right answer

OTC is not the superior option in general, and it is worth being clear about when it is not.

For ordinary amounts, the exchange route is cheaper, faster and involves fewer people. If you already hold a verified account and the amount sits comfortably within the book, using a desk adds process for no benefit.

Exchanges also offer things a desk does not: limit orders, the ability to work an order over time, and price discovery you can watch. If you have no deadline and want to sell into strength, that flexibility is worth more than a firm quote.

The honest summary is that these are different tools. The order book is a good mechanism until your own order becomes a meaningful share of it, and a poor one immediately afterwards.

Where Arclight Pay fits

Arclight Pay is currently in pre-launch and is not providing financial services. The service being prepared is OTC conversion between supported digital assets and fiat, with eligible proceeds settled to a verified bank account held in the customer's own name.

Nothing in this guide is a recommendation to trade, or advice about how or when to do so. Digital assets carry material risks including the loss of value; read the risk disclosures before using any service of this kind.