Ilman leimaa paperi ei ole voimassa.

Ilman means without and it behaves like a preposition/postposition in Finnish. It requires the partitive case:

• ilman leimaa = without (a) stamp You’ll see the same pattern in:
• ilman sokeria (without sugar)
• ilman rahaa (without money)

• leima is the dictionary form (nominative).
• leimaa is the partitive singular, required by ilman.
• leiman (genitive) is generally not used after ilman in modern standard Finnish (you may occasionally see genitive in older/poetic language, but the normal rule is partitive).

So ilman leimaa is simply the standard grammatical form.

Finnish negation uses a separate negative verb that conjugates for person/number:

• ei = 3rd person singular (he/she/it does not)

After the negative verb, the main verb appears in the connegative form:

• olla (to be) → ole

So:

• (paperi) ei ole = is not

Compare:

• paperi on voimassa (the paper is valid/in force)
• paperi ei ole voimassa (the paper is not valid/in force)

Not every negative sentence forces a partitive subject. Here, paperi is the clear, definite subject of a normal copula sentence (X is not Y), so nominative is natural:

• Paperi ei ole voimassa.

Partitive subjects are especially common in existential or “there is/are”-type sentences, or when the subject is indefinite/amount-like:

• Täällä ei ole paperia. (There is no paper here.)

Voimassa is the inessive case form of voima (power/force):

• voima → voimassa = literally in force

In modern Finnish it’s very commonly used as part of the fixed expression:

• olla voimassa = to be valid / to be in force

So voimassa functions like an adverbial complement meaning “in effect/valid.”

Yes, olla voimassa is a very common set phrase, especially for laws, rules, documents, tickets, permits, etc.

Depending on context, alternatives include:

• ei päde (doesn’t apply / isn’t valid) — common but slightly different nuance
• ei kelpaa (isn’t accepted) — more about acceptance than legal validity

But ei ole voimassa is often the safest for “not legally/officially valid.”

Finnish word order is flexible. Putting Ilman leimaa first highlights the condition (“without a stamp…”).

You can also say:

• Paperi ei ole voimassa ilman leimaa.

Both are correct; the difference is mostly emphasis and information flow.

By itself, ilman leimaa is usually interpreted as without a stamp (at all) in the relevant sense. Finnish doesn’t have articles (a/the), so specificity comes from context.

If you want to emphasize “without any stamp whatsoever,” you can add:

• Ilman mitään leimaa paperi ei ole voimassa. (Without any stamp, the paper is not valid.)

Past:

• Ilman leimaa paperi ei ollut voimassa. (was not valid)

Future / “will not be valid” (common ways):

• Ilman leimaa paperi ei ole voimassa. (often still used if it’s a general rule)
• Ilman leimaa paperi ei tule voimaan. (will not enter into force / will not become valid)

A few helpful points:

• Stress is usually on the first syllable: IL-man LEI-maa PA-pe-ri ei O-le VOI-mas-sa
• ei is pronounced like “ay” in say (roughly).
• Double vowels are long: lei-maa has a long aa at the end.
• voimassa has clear syllables: voi-mas-sa (with ss pronounced longer than a single s).