Application by appellant for a writ of mandamus to compel the respondent. bank, as county depositary for Marengo county, to pay a warrant drawn by the commissioners’ court in favor bf B. E. Whitcomb, and by him assigned to appellant. The parties agree that it shall be considered for the purpose of this case that appellant has the same right to relief that his assignor would have had in the absence of an assignment. In the trial court the application was denied, after which this appeal. The facts are stated in the trial court’s opinion and judgment, which will be reproduced in the report of the case.

[1, 2] In section 1 of the act of September, 25, 1919 (Acts, p. 722), it was provided that courts of county commissioners, boards of revenue, and other governing bodies of counties, should have authority to adopt the “budget system” for the conduct of county affairs, and to that end appropriate from the county treasury “sufficient funds to pay the actual expenses” as shown by the budget so adopted. With or without this declaration of legislative purpose it was competent for commissioners’ courts and boards of revenue, if necessary or expedient in the exercise of that part of the sovereign legislative and administrative power of the state previously committed to them, to adopt the “budget system,” and to apply the whole revenues in each year to current governmental county expenses, leaving nothing to be applied in payment of old debts. White v. Decatur, 119 Ala. 476, 23 South. 999. Section 2 of the act recognizes the fact that where holders of passed and allowed claims against the county have stipulated for a lawful rate of interest, such rate cannot be lowered unless with the consent of the holders. Bryan v. Moore, Minor, 377; 22 Cyc. 1521. Section 3 appears to be but another declaration in part of the existing law; but it provides that—

Passed and allowed claims “shall be paid as soon as the condition of the county treasury shall warrant their payment out of any funds available for such purpose and not actually necessary for the current expenses of the county as shown by said budget.”

True, the act postpones the payment of previously passed and allowed claims to current expenses “as shown by said budget”; but the claims thus preferred are, in effect, defined by the section as claims arising out of the actually necessary conduct and operation of county affairs during; the current year. On the one hand, we do not see that anything is accomplished by the act; on the other, we see on its face no tenable objection to its validity.

*670 [3] The real question presented by the record is this: Whether under the act above referred to or previous law the commissioners’ court of Marengo county had authority to defer payment of petitioner’s claim, passed and allowed four years before, until all the items of current county expense shown by the budget should be paid, and we apprehend that, while the budget may be looked to as an official ascertainment and declaration of those expenses which are necessary to the proper discharge of the governmental functions of the county, and the estimated revenues to meet them, such expenses, so far as legal right is concerned, would just as well have been preferred without the budget, for in any event only the surplus of income, after current governmental expenditures have been met or provided for, can by process of law be applied in payment of petitioner’s claim. White v. Decatur, supra. If the fact were that the commissioners’ court had levied taxes to the limit of its authority — and as to that no question is raised in this ease— and the county’s entire income were necessary to meet its legitimate expenses for governmental purposes, and there were no surplus in the treasury' to the credit of the general fund of the county, petitioner could only await the time when the proper conduct of county affairs would produce a surplus from which he might be paid. J. B. McCrary Co. v. Brunson, 204 Ala. 85, 85 South. 390.

[4-8] The record shows the items and the sum of the expenses provided for by the order of the commissioners’ court. We need not examine them seriatim. It is enough to say that in the list the court included an item of $8,400 for annual interest on road warrants — far more than enough to pay petitioner’s warrant, which was for $21.25. There was also to the credit of the general fund far more than enough to pay petitioner’s warrant in its turn, had not that fund by the orders of the commissioners’ court been transferred on the books of the county depositary to the credit of the items of expense shown by the budget. It is the duty of the county treasurer—

“to number and register, in the order in which they are presented, all claims against the general fund which have been audited and allowed by the court of county commissioners as claims against such fund, such register showing the number of the claim, the date presented for registration, to whom allowed, when allowed, the character of the claim and the amount thereof; and, except as otherwise provided by law, pay the same in the order of their registration.” Code § 211, subd. 4.

To the duties and obligations of the county treasurer the county depositary', appellee, has succeeded. The provisions of the statute affecting the means and order of payment became a part of the contract between the parties. Commissioners’ Court v. Rather, 48 Ala. 433. The obligation of the contract, including the remedy for its enforcement, could not be impaired by statute, and, such being the case, its obligation could not be impaired by the county authorities (Board of Revenue v. Farson, 197 Ala. 375, 72 South. 613, L. R. A. 1918B, 881), exercising only such powers as are delegated to them by the Legislature. Askew v. Hale County, 54 Ala. 639, 25 Am. Rep. 730. The obligation of a contract is impaired when the remedy for its enforcement is postponed or retarded without the substitution of a substantial equivalent: Osborn v. Johnson Wall Paper Co., 99 Ala. 313, 13 South. 776, and authorities cited. At the time of the presentation of petitioner’s claim for payunent, four years after its registration, the Qounty was in funds, out of whicn, in its turn, his claim should have been satisfied. The effort on the part of the commissioners has been to convert the fund out of which petitioner was entitled to payment into a fund for the payment of interest only' on road warrants, and thus to deprive him of his preference under the law as it existed at the time of the contract between the parties. We are not informed whether the debt, for the payunent of the interest on which the sum of $8,400 is set apart in the budget, is a debt the principal of which, or the interest only, will fall due during the year; but, whatever may be the fact as to that, it is clear that such debt is not a current expense of administering the county government, and the commissioners’ court had no right to set apart to its exclusive payment any part of the revenues so as to defeat petitioner of his right to subject the excess over necessary current expenditures to the satisfaction of his claim, payable in the order of its registration. White v. Decatur, supra; Anniston v. Hurt, 140 Ala. 394, 37 South. 220. The necessary effect of the orders made in the premises by the commissioners’ court, as the trial court found, was to postpone petitioner’s warrant and make the time of its payunent wholly indefinite and uncertain.

[9] Counsel refer to the act of September 22, 1915 (Acts, p. 573), which authorized the transfer of any surplus of the general fund to the road fund. But that act is of no consequence in this connection, for the reason that there could be no surplus of the general fund as long as there were unpaid claims, audited, allowed, and registered, outstanding against it.

Nor does the decision in Harold v. Herrington, 95 Ala. 395, 11 South. 131, help the contention against the petitioner in this case. That case was concerned about the fine and forfeiture fund of a county, a fund in which “nobody has, or can have, a vested right to share in or be paid out of, since the right so to do, when it is accorded by the Legislature, is a matter of mere grace and expediency.” *671 Here, as we have written, contract rights are involved, and are beyond the reach of legislative interference.

We will not be understood as speaking of the' operation' of the orders of the commissioners’ court on claims audited, allowed, and registered subsequent to such orders. That question is not presented. Nor does it appear to us that the language of the act of September 25, 1919, needs be construed as intending anything contrary to what has been written in this case. The trouble has been in the too broad interpretation of its powers by the court of county commissioners.

Our conclusion is that the orders of the commissioners’ court on the authority of which the county depositary refused to pay petitioner’s warrant, in so far as they purported to affect the time and manner of the payment thereof, were and are invalid, and that, in consequence, petitioner was and is entitled to the relief prayed.

Reversed and remanded to the trial court, where judgment will be rendered in accordance with this opinion.

Reversed and remanded.