A farm was searched in the Banbridge area on Tuesday morning by officers from Her Majesty's Revenue and Customs (HMRC).
A computer, documents and records were seized.
John Whiting, HMRC's Assistant Director Criminal Investigation, said: "HMRC takes tax fraud extremely seriously and anyone deliberately choosing to evade the taxes they owe should expect not only a heavy fine, but possibly a criminal prosecution as well.
"Anyone with information about people who may be involved in tax fraud can contact the Tax Evasion Hotline on 0800 788 887."
The pair were questioned by HMRC officers.
Investigations are continuing.