A crypto buy order with a limit price can trade immediately and incur a taker fee. The limit controls the highest purchase price; it does not, by itself, require the order to wait in the order book. Post-only is a separate instruction that changes that outcome.
| What you need to know |
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| A buy limit is a price ceiling; a sell limit is a price floor. |
| A limit order that immediately matches an existing order can incur taker fees. |
| Post-only prevents that immediate match under the documented Kraken and Coinbase rules. |
| Available quantity and execution instructions determine whether the whole order fills. |
Kraken’s limit-price explanation distinguishes a buy price below the lowest sell offer from one that matches an existing offer. The latter can execute straight away. Its price protection still applies: a buy cannot execute above its limit, even when more expensive sell orders are available.
This is a distinction between two functions. A price limit defines acceptable prices. Maker or taker describes whether an execution adds liquidity by resting first, or takes liquidity already offered. Calling an order a limit order does not settle the second question.
The same price cap produces two different outcomes
Consider an illustrative order book, not a live bitcoin quote. Sellers offer 0.02 BTC at €50,000 per bitcoin and another 0.03 BTC at €50,010. A buy order requests 0.04 BTC with a €50,000 limit and allows immediate matching. Assume the offers do not change while it arrives.
At that unchanged price cap, only the first 0.02 BTC can execute, costing €1,000 before fees. The remaining 0.02 BTC cannot buy the next offer because €50,010 exceeds the limit. The cap has worked even though half the requested quantity remains unfilled. Under a good-til-cancelled instruction, that remainder can wait for another matching seller.
Change only the execution instruction to post-only. The same €50,000 buy would immediately match the existing sell offer. Kraken describes cancelling a post-only buy in that situation; Coinbase’s spot-order instructions specify rejecting the entire order if any part would execute immediately. That produces no accepted resting order, rather than the partial purchase in the first example.
Coinbase also explains how a regular order can involve both fee classifications: an immediately executed portion attracts taker fees, while a remainder that rests can attract maker fees if it later fills. This does not establish either platform’s current fee rate or make the total cost equal across platforms.
The documentation was checked on 23 October 2026. A post-only rejection therefore needs to be read differently from an unfilled resting order: the former has failed the immediate-match condition, while the latter is still waiting for matching liquidity. Neither a price cap nor maker status guarantees a completed purchase.
