Watch the webinar below, James Caw and Bitcoin tax specialist Tertius discuss the mechanics of buying Bitcoin at scale, including what actually happens to your effective price in practice.
Many investors assume that once a Bitcoin purchase gets large enough, the obvious next step is an OTC desk.
That assumption is understandable. It sounds professional. It sounds like what serious buyers do. And OTC does offer real, meaningful advantages in certain situations. But in our own experience, across real negotiations with top platforms and OTC desks, it does not automatically deliver the best execution. Not even close.
That is worth understanding before you commit to a large trade.
This article is general educational content. It does not constitute financial advice, and execution outcomes vary based on market conditions, liquidity, timing, trade size, provider structure, and how the order is managed.
What Happens When You Try to Buy a Large Amount on a Retail Exchange
The standard concern about buying large quantities of Bitcoin on a retail exchange is slippage, the idea that a large market order will push the price up as it works through the order book, so that the later portions of the trade execute at worse prices than the first.
That concern is real, and it matters most in specific conditions: where the order book is thin, where the trade is executed as a single immediate market order, and where the size is genuinely large relative to available liquidity. In those circumstances, a buyer working through available offers one after another will see the price move against them as they go.
The important qualifier is what “thin” and “genuinely large” mean in practice. Major Bitcoin exchanges, and South African-based platforms that route orders into global liquidity, maintain substantial order depth, particularly during normal market hours. A purchase worked as a structured order rather than a single market sweep may experience far less slippage than people expect.
The assumption that retail exchange routes are categorically inappropriate for large buyers is worth examining rather than accepting at face value.
What OTC Actually Is and What It Offers
An OTC (over-the-counter) transaction is a trade negotiated directly between a buyer and a provider, a desk that holds Bitcoin inventory or sources it specifically for the transaction, at an agreed price, outside the public order book.
The two real advantages OTC offers are worth being clear about.
Discretion. An OTC trade does not appear in the public order book. If you are a large buyer and you do not want the market to know you are buying, because a visible large order could signal intent and potentially move price ahead of your execution, OTC offers that privacy. The transaction happens off-exchange, privately, between counterparties.
Price certainty. An OTC quote gives you a known price before you commit to the trade. You agree to buy a specific amount of Bitcoin at a specific price, and that price is locked at execution. You know exactly what you are paying before you send funds. That certainty has genuine value for some buyers, particularly those managing treasury positions, reporting costs to a board, or operating under governance frameworks that require a known transaction price.
Those are real benefits. The question is whether they come with a cost, and what that cost is relative to the alternative.
What OTC Does Not Automatically Offer: Better Execution
Here is where our own experience differs from the common assumption.
We have negotiated OTC deals with top platforms and OTC desks. The quoted margins in those negotiations often looked very tight, competitive, sharp, and apparently hard to improve on. On paper, the rates looked good.
When we compared those quoted OTC rates to the actual average price achieved through our auto-buy trading platform, the live execution consistently came out better.
The reason is straightforward, and it is worth understanding mechanically. An OTC desk quotes you a fixed price. That price is set at a specific moment in time and includes the desk’s own margin, their cost of sourcing the Bitcoin, their hedging costs, their profit, and a buffer for their own risk. Even when that margin looks small, it is still there.
When you execute through a live market system, particularly one that works an order over time rather than hitting the book in a single sweep, the outcome depends on what the market does during execution. If the market moves in your favour during that window, you benefit from it. Your effective average price can end up lower than the best OTC quote you were offered.
That is what consistently happened in our experience. The live market moved in our favour during execution often enough, and our platform was able to source volume efficiently enough, that the effective average acquisition price came out below the OTC desk’s best offer.
That does not mean this outcome is guaranteed in every trade or every market condition. It means that the assumption of OTC superiority for large buyers is not something we found to be true in practice, and that the quoted rate is not the same as the final effective price.
The House Often Wins in OTC: A Practical Observation
There is a structural reality in OTC execution worth naming directly.
An OTC desk is a business. Its job is to source Bitcoin and sell it to buyers at a price that covers its costs and produces a return. Even when the quoted spread appears tight, the desk’s economics are built into the quote. In many OTC transactions, the desk still needs to protect its own economics, so the buyer should not assume that a tight quote automatically means the best possible execution.
What this means in practice is that the desk’s business model is built around consistently managing their side of the trade well. That is not a criticism, it is simply how the business works. But it does mean that a buyer focusing only on the visible quoted rate may be missing a more complete picture of where value is actually being captured in the transaction.
The buyer’s job is to think about execution quality from their own side: not just what the rate looks like on a quote sheet, but what the effective average price turns out to be when the trade settles.
How Auto-Buy Execution Actually Works
For context on the comparison, it helps to understand briefly how a structured auto-buy or systematically worked execution differs from a single market order.
A large trade worked through a live market is typically not executed as one instant order. Instead, it is broken into smaller tranches and worked over a period of time, minutes, hours, or sometimes longer, to reduce the market impact of any single order while capturing volume as it becomes available at different price points.
This approach does several things. It reduces the risk of a single large order sweeping through available liquidity and moving price significantly. It allows the execution to benefit from price variation during the window, if price dips during execution, later tranches buy at a lower level. And it allows the system to adapt to liquidity conditions as they change in real time.
The key metric at the end of this process is the volume-weighted average price (VWAP), the effective average price at which all the Bitcoin was acquired across the full execution window. That is the number that matters, not the price at the moment the first tranche went through.
In our experience, the VWAP achieved through our auto-buy process has consistently compared favourably to OTC quoted rates, even when those quoted rates looked sharp at the time. That outcome is driven by market conditions being variable, execution systems being able to take advantage of that variability, and the live market not always moving against a patient buyer.
The Record-Keeping and SARS Dimension
For South African investors, there is a practical SARS dimension to large trades worth noting alongside the execution question.
OTC trades have one useful record-keeping property: a single agreed price. Your cost basis is clear, you bought a specific quantity of Bitcoin at a specific price, on a specific date, through a single documented transaction. That simplicity has administrative value. When your tax practitioner asks for your acquisition cost, the OTC route gives you a clean single number.
Live market execution worked over time produces a blended cost basis across multiple smaller transactions. The effective average price is what matters for tax purposes, and a good provider will give you documentation of all the individual transactions that make up the total acquisition. That documentation is slightly more complex to present than a single OTC trade confirmation, but it is entirely workable.
This is not a reason to choose OTC, but it is a genuine consideration, particularly for investors holding Bitcoin inside a company or trust where clear accounting records matter for reporting and governance purposes.
Whatever execution method you use, the documentation of your rand acquisition cost is essential for correct SARS reporting. SARS taxes disposals based on the difference between your acquisition cost and your proceeds, both measured in rand at the time of the relevant transaction. Clean records from the point of purchase, regardless of execution method, are the foundation of a clean tax position.
When OTC Actually Makes Sense
Given everything above, there are specific situations where OTC makes real sense for a large Bitcoin buyer, and it is worth being honest about what those situations are.
Where confidentiality is the priority. If you are a family office, a company, or a high-net-worth individual who does not want buying activity to be visible to other market participants, OTC provides that privacy. A large order executed through the live order book is visible to anyone watching the market in real time. An OTC trade is not.
Where a fixed price matters more than the best possible price. If you are presenting a Bitcoin purchase to a board, reporting a cost to investors, or operating under governance that requires a known price at the time of execution, OTC delivers that certainty. A locked quote is a locked quote. The fact that live execution might have produced a better outcome is beside the point if your governance framework requires a definitive, pre-agreed price.
Where trade size genuinely exceeds available exchange liquidity. In thin markets, at very large sizes, or during periods of significant volatility, there are circumstances where the order book may genuinely not be able to absorb a large order without significant price impact. In those conditions, an OTC desk with access to inventory may be the more practical route.
Where speed matters more than optimisation. If a buyer needs to execute a large transaction immediately, for a time-sensitive business or treasury reason, OTC can be faster to execute than a worked order spread over time.
These are real use cases. OTC is not a poor product. It solves specific problems well. The point is that “large purchase” on its own is not sufficient reason to assume OTC is automatically the right route.
When Live Execution Is Worth Considering
For investors whose primary goal is the lowest effective average acquisition price, who care most about where Bitcoin ends up on their books relative to what they paid, a carefully executed live market approach may serve them better, particularly in the following conditions.
Where market conditions during execution are likely to be variable. A live market that moves up and down during an execution window gives a patient, systematic buyer the opportunity to capture dips that a fixed OTC quote cannot accommodate.
Where the provider’s execution infrastructure is good. The quality of live execution depends on how well the order is managed, how it is sized, how it is timed, and how it adapts to market conditions in real time. A well-managed execution process working a large order thoughtfully is a different thing from a buyer hitting the book themselves with a single market order. The comparison should be between a professional execution process and an OTC deal, not between a clumsy large order and a polished desk.
Where the priority is long-term accumulation rather than a single-event purchase. Dollar-cost averaging at scale, buying regularly over time using a systematic auto-buy, is a form of live market execution that averages price over a longer window. Our experience is that this approach, applied consistently with a marginal fee structure, has produced strong outcomes over time relative to the OTC alternatives we have tested.
What Our Own Testing Found
To be direct about what we found: when we negotiated with major platforms and OTC desks for significant purchases, the quoted rates were genuinely competitive. The desks did not price in large visible margins. On paper, the deals looked sharp.
But when we measured the outcomes against our auto-buy execution across comparable periods and volumes, the auto-buy consistently delivered a lower effective average acquisition price.
The explanation is not that the OTC desks were operating in bad faith. It is that the live market moved in our favour during execution, and our platform was able to capture that movement. The OTC desk’s quoted price, however tight, was fixed at a moment in time. Our execution was not.
That observation does not hold in every market condition. In a rapidly rising market during an execution window, live execution works against the buyer. Price rises as you buy, and a locked OTC quote would have been the better outcome. The result depends on what the market does, and no one can predict that reliably in advance.
What we can say is that in our own testing and experience, the assumption of OTC superiority for large purchases did not hold. And that finding, which runs counter to common wisdom in this space, seemed worth sharing plainly.
The Right Questions Before a Large Purchase
For any investor approaching a significant Bitcoin purchase, the question is not simply “should I use OTC?” It is a more specific set of questions worth working through.
Do I care more about execution privacy or the best possible average price? If privacy is the primary concern, OTC addresses it. If price is the primary concern, execution quality matters more than the desk’s headline quote.
Do I need a locked price for governance or reporting purposes? If yes, OTC solves that problem directly. If not, the benefit of price certainty may not justify the potential cost.
What is my time horizon for this purchase? A patient buyer who can work an order over time is in a fundamentally different position from one who needs to transact immediately. The more flexibility you have, generally the more favourably live execution can be managed.
What does the execution record actually show? If you have access to data on past purchases, what your average acquisition price was and how it compared to market alternatives at the time, that data is more useful than general claims about OTC versus exchange execution. Let the evidence lead.
How is the market behaving right now? Execution quality is always contextual. A systematic approach applied during stable or declining markets produces different outcomes than the same approach during a sharp price rise. Knowing the market environment you are operating in is part of the decision.
Final Thought
OTC has a legitimate place in Bitcoin execution. Discretion and price certainty are real benefits, and for some buyers in some situations, they are exactly what matters most.
But OTC is not automatically the right choice for every large purchase, and the quoted rate is not the same as the effective execution outcome. In our own experience, tested and measured against live alternatives, the auto-buy approach consistently delivered a lower effective acquisition price than the best OTC deals we negotiated.
That is an honest finding. It does not generalise perfectly to every market condition or every buyer. But it is worth knowing before you assume the professional-sounding option is necessarily the better-performing one.
The right execution method is the one that delivers the outcome you actually care about, whether that is price, certainty, privacy, or some combination of all three. Getting clear on your own priorities before you transact is the most useful thing you can do.
This article is general educational content only. It does not constitute financial, investment, tax, or exchange control advice. Execution outcomes depend on market conditions, liquidity, timing, trade size, provider structure, and custody arrangements. Past execution comparisons do not guarantee future results. SimplB is an FSCA-licensed Bitcoin service provider, contact us to discuss your specific situation.
