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Collins English Dictionary/Thesaurus gives the following equivalents for TAMPER:
alter, damage, fiddle (Inf.), fool about (Inf.), interfere, intrude, meddle, mess about, monkey around, muck about (Brit. sl.), poke one's nose into (Inf.), tinker
I reckon that FORMULARZ SFAŁSZOWANY gets closest to the original meaning.
The asker has declined this answer Comment: formularz nie jest sfalszowany (tampered), ale ujawnia probe
Explanation: Tamper-evident doesn't mean "sfalszowany". It means that the form
possesess some means which permit finding out if there were attempts to falsify it (kind of coating, label, type of paper etc):