Definition
Tokenization tax is the extra token count, monetary cost, latency, or lost context capacity imposed when a tokenizer represents equivalent content less efficiently in one language, script, programming language, domain, or notation than another. It is commonly measured with token fertility, such as tokens per word, or with a ratio against a reference language or tokenizer.
Distinguish it from nearby terms
This is not a provider surcharge printed on a price sheet. The same per-token price creates unequal effective prices when equivalent meaning requires different token counts. Higher token counts also do not prove that tokenization alone caused a quality gap, because training-data coverage and model architecture can confound comparisons.
Check your understanding
Compare parallel content across the exact tokenizers and models you plan to use, then report cost, latency, context consumption, and task quality separately.