Opinion by
Kephakt, J.,
The City of Pittsburgh leased from the appellee certain premises, by an agreement which,contained the following clause: “It is......agreed further that the City of Pittsburgh is also to pay all city taxes, or assessments, made against said property by the city, and make all improvements at its own cost and expense.” Sewer and paving were laid in front of the leased premises, assess-*376merits for which were duly made,. liens therefor were filed, and a scire facias sur municipal lien issued thereon; service was had on the defendants in the writs and judgment taken in default of an appearance. These judgments were paid by the plaintiffs without execution, and afterwards they brought this action to recover.
. The use of the word “assessment” in the foregoing paragraph, included an assessment for grading, paving, curbing^nd construction of sewers: Griffen, Smith & Co. v. Phœnix Pottery Co., 14 W. N. C. 266; Delaware & Hudson Canal Co. v. Von Storch, 196 Pa. 102. It is not synonymous with the word “taxes”: Pray v. The Northern Liberties, 31 Pa. 69; Pettibone, et al., v. Smith, 150 Pa. 118. Nor was it the intention to use it in such sense in the lease. Council approved the lease by a resolution which is sufficiently clear to identify the lease in question, and such approval embraced all the covenants contained in it. We do not regard the covenant “to pay for all assessments” as a defense by way of a set-off ¡in the proceeding by the city on the scire facias for .the sewer assessment.
“The foundation of set-off” or equitable defense “is the preyention of circuity of action,” and the “general rule is that, cross demands must be between the same persons and in the same rights, so that actions may be maintained thereon each against the other”: Hibert v. Lang, 165 P.a. 439. There must be mutuality of demánd, both as regards the quality of the right and the identity of the parties: Stuart v. Commonwealth, 8 Watts 74. In not every instance where the right of action exists may it be said that the right of set-off will be allowed; ..The.quality of the matter proposed to be set off may be.of.-such character as to be sustainable pnly by separate action. The remedy here provide^ is.stqjmtoix tp.enforce a species, of taxation. It is justified, as., a of public policy. The property owner is permittethonly such defenses am thorized by statute: Scranton v. Jermyn, 156 Pa. 107. It may be, said, generally, as1 to liens of this kind, assigned *377by tbe municipality, any defense arising directly from tbe subject-matter of tbe improvement will be. allowed. Thus, in assigned claims, damages for the careless or. unskillful manner in which the public improvements are constructed may be set off: Charlton v. Allegheny City, 1 Grant 208; Philadelphia, to use, v. Bilyeu, 47 Pa. Superior Ct. 148. Claims for materials may be set off: York City, to use, v. Miller, 60 Pa. Superior Ct. 407. There is a distinction between claims enforced by use-plaintiffs and those sued for by the municipality: Pepper v. Philadelphia, 114 Pa. 96. “It is almost universally held that in an action for taxes set-off of an indebtedness of the state or municipality to the tax debtor will not be allowed, the statutes of set-offtbeing construed in the light of public policy as not allowing the remedy in proceedings for this purpose, nor is such a claim subject to compensation”: 34 Cyc. 656. The same should be true as to municipal liens for improvements. It can readily be seen how a defense such as here proposed, in a proceeding depending on statute, with an appropriation of funds for a specific amount by a legal body from money usually secured by an issue of bonds as the basis of its action, might involve the city in many collateral questions which would work a great injustice to and seriously interfere with its rights. The city depends on the amount realized from the bonds and the assessments due from property owners to pay for the improvement. This money could not be diverted by The city and it must be if this defense were allowed: Major v. Aldan Borough, 209 Pa. 247; Pittsburgh v. Harrison, 91 Pa. 206; Brientnall v. Philadelphia, to use, 103 Pa. 156; Erie City v. Butler, 120 Pa. 374. If the city owed several months’ rent this could not be used as a set-off to a lien for taxes: McCracken v. Elder, 34 Pa. 239; Hopper v. Pittsburgh, 5 Pa. Superior Ct. 41, 45: Tagg v. Bowman, 99 Pa. 376-379. Nor should it be to a lien for municipal improvements.
The plaintiffs’ claim is for a breach of the covenant in *378the lease. This condition arose when the breach occurred and not before. No right of action existed until they were compelled to pay. A set-off cannot be allowed until the counter right of action has accrued: Pennell v. Grubb, 13 Pa. 551. The city did not violate the contract until it exacted the money from the plaintiffs. The set-off was not complete when the scire facias was sued out.
Considering the questions in the light of public policy, and as affecting an important feature of municipal administration, claims arising from independent transactions for set-off against liens for public improvements sued on by the municipality, should not be allowed.
Judgment affirmed.