Conn. Practice Book § 10-70

(a) In any action to foreclose a municipal tax or

assessment lien the plaintiff need only allege and

prove: (1) the ownership of the liened premises

on the date when the same went into the tax

list, or when said assessment was made; (2) that

thereafter a tax in the amount specified in the list,

or such assessment in the amount made, was

duly and properly assessed upon the property and

became due and payable; (3) (to be used only

in cases where the lien has been continued by

certificate) that thereafter a certificate of lien for

the amount thereof was duly and properly filed

and recorded in the land records of the said town

on the date stated; (4) that no part of the same

has been paid; and (5) other encumbrances as

required by the preceding section.

(b) When the lien has been continued by certificate, the production in court of the certificate of

lien, or a certified copy thereof, shall be prima

facie evidence that all requirements of law for the

assessment and collection of the tax or assessment secured by it, and for the making and filing

of the certificate, have been duly and properly

complied with. Any claimed informality, irregularity

or invalidity in the assessment or attempted collection of the tax, or in the lien filed, shall be a

matter of affirmative defense to be alleged and

proved by the defendant.