This appeal raises the question whether the custodial mother of two minor children, ages fourteen and thirteen, whose sole source of income is means-tested public assistance,1 can be deemed to be voluntarily unemployed and thereby have an income imputed to her as the basis for her child support obligation to a noncustodial third child. The statutorily authorized Michigan Child Support Formula Manual prohibits the imputation of means-tested public assistance benefits as income. While a trial court may enter an order of support that deviates from the formula, it may not do so without setting forth in writing or on the record why following the formula would be unjust or inappropriate.2 Additionally, this Court has required the trial court to evaluate a num*192ber of factors in determining the actual ability and likelihood of earning the imputed income. Sword v Sword, 399 Mich 367; 249 NW2d 88 (1976). The Michigan Child Support Formula Manual also requires the evaluation of certain equitable factors when deciding to impute income. In the instant case, the trial court failed to comply with these requirements. Accordingly, we reverse the judgment of the Court of Appeals and remand this case to the trial court for a new calculation of the support order.
i
Plaintiff James Ghidotti and defendant Brenda Barber are the parents of James Allen Ghidotti, Jr., bom November 30, 1987. The parties were never married. Judge Kingsley of the 37th Circuit Court granted physical custody of James Jr. to his father, the plaintiff, on May 18, 1993.
Defendant has custody of two minor daughters, ages fourteen and thirteen, from a previous marriage. The father of the two girls, defendant’s ex-husband, is incarcerated and does not pay child support. At the time this case was before the trial court, defendant and her daughters received $356 a month in Aid to Families with Dependent Children benefits. At the same time, plaintiff earned approximately $370 a week from employment.
Pursuant to an order from the trial court, the friend of the court for Calhoun County conducted a child *193support review of defendant’s obligation to her noncustodial son, James Jr. The friend of the court prepared two recommendations regarding defendant’s child support obligations.3 The first recommendation, which was based on defendant’s actual income, set the support level at $0.00. When calculating the second recommendation, the friend of the court determined that defendant did not suffer from any condition or restriction that would preclude her from obtaining gainful employment. Accordingly, the friend of the court deemed defendant to be voluntarily unemployed and calculated an imputed income for defendant equaling $170 a week. The imputed income equaled what defendant would earn if she worked at a minimum wage job for forty hours a week. The second recommendation, which was based on defendant’s actual income, plus her imputed income, set defendant’s child support obligation at $33 a week; *194this amount included $22 a week for child support and $11 a week for child care.
On May 16, 1994, the trial court heard testimony regarding the child support review. Defendant argued that, because she was receiving afdc and food stamp support for her other two children, she could not be required to pay child support. The court disagreed and set the level of child support at $33 a week, imputing income to defendant and adopting the second calculation of the friend of the court.
Defendant appealed this ruling, but the Court of Appeals denied leave. This Court remanded the case to the Court of Appeals as on leave granted. 449 Mich 861 (1995). The Court of Appeals affirmed the trial court’s award of child support at the rate of $33 a week, holding that
the fact that a party receives an afdc grant is irrelevant when determining whether a parent is voluntarily unemployed and the amount of child support that a voluntarily unemployed noncustodial parent will pay for the benefit of the noncustodial child. [222 Mich App 373, 380; 564 NW2d 141 (1997).]
Defendant appealed the ruling of the Court of Appeals, and this Court granted leave on April 1, 1998. 456 Mich 959.
n
At the time this case was decided, defendant was a recipient of AFDC, which the federal welfare program was called at that time. The Personal Responsibility and Work Opportunity Reconciliation Act, Pub L 104-193, 110 Stat 2105 (codified as 42 USC 601-1788), replaced afdc with Temporary Assistance for Needy *195Families (TANF), as part of the federal welfare reform program enacted in 1996. Because the Michigan Family Independence Agency has elected to use TANF funds as afdc funds were used previously, to provide cash assistance to needy families with minor children, the analysis of defendant’s situation remains the same.
The stated purpose of TANF can be found at 42 USC 601(a), which provides:
In general. The purpose of this part [42 USC 601 et seq.] is to increase the flexibility of States in operating a program designed to—
(1) provide assistance to needy families so that children may be cared for in their own homes or in the homes of relatives;
(2) end the dependence of needy parents on government benefits by promoting job preparation, work, and marriage;
(3) prevent and reduce the incidence of out-of-wedlock pregnancies and establish annual numerical goals for preventing and reducing the incidence of these pregnancies; and
(4) encourage the formation and maintenance of two-parent families.
In order to receive federal funds under the tanf program, a state is required to “establish guidelines for child support award amounts within the State.” 42 USC 667(a). This statute also requires that
[tjhere shall be a rebuttable presumption, in any judicial or administrative proceeding for the award of child support, that the amount of the award which would result from the application of such guidelines is the correct amount of child support to be awarded. A written finding or specific finding on the record that the application of the guidelines would be unjust or inappropriate in a particular case, as determined under criteria established by the State, shall be suffi*196cient to rebut the presumption in that case. [42 USC 667(b)(2).]
The Legislature complied with these requirements when it enacted MCL 722.717(3); MSA 25.497(3), stating that “the court shall order support in an amount determined by application of the child support formula developed by the state friend of the court bureau.”4 The statute goes on to state that the court may enter an order of support that varies from that mandated by the guidelines, but only if the court determines from the facts of the case that application of the child support formula would be unjust or inappropriate and sets forth in writing or on the record the following:
(a) The support amount determined by application of the child support formula.
(b) How the support order deviates from the child support formula.
(c) The value of property or other support awarded instead of the payment of child support, if applicable.
(d) The reasons why application of the child support formula would be unjust or inappropriate in the case. [MCL 722.717(3); MSA 25.497(3).]
The Friend of the Court Bureau has written, distributed, and frequently revised the Michigan Child Sup*197port Formula Manual pursuant to this legislative mandate.
The relevant language of the manual states:
Imputation is not appropriate where:
1. A payee/payer source of income is a means tested income such as Temporary Assistance to Needy Families (tanf), Family Independence Payments (fip) (formerly afdc), Food Stamps, Supplemental Security Income (ssi), etc. [Michigan Child Support Formula Manual, tenth rev, p 8 (emphasis in the original).]
m
In reaching its decision in the present case, the Court of Appeals recognized the prohibition contained in the manual against imputation of means-tested public assistance benefits as income.5 However, while acknowledging that defendant had no source of income other than afdc and that this could not be counted as income for the purpose of a child support calculation, the Court of Appeals upheld the trial court’s decision to deem defendant as voluntarily unemployed and thereby able to work:
[The court] apparently viewed [defendant] as it should and does view all unemployed yet employable noncustodial parents who, for one reason or another, have no job and claim an inability to financially support a child. [222 Mich App 377-378.]
The trial court’s decision that defendant was employable was based on the finding of the Calhoun County Friend of the Court’s investigation that she “suffered *198from no condition or restriction that would preclude her from obtaining gainful employment.” Id. at 375.
The Court of Appeals approval of imputation of income to a parent in defendant’s situation is based on a misunderstanding of the applicable statutes and case law.
A
According to the applicable statutes, the child support formula “shall be based upon the needs of the child and the actual resources of each parent.” MCL 552.519(3)(a)(vi); MSA 25.176(19)(3)(a)(vi). In applying this mandate, cases have broadened the limits of “actual resources” to include certain payers’ unexercised ability to pay. See, e.g., Rohloff v Rohloff, 161 Mich App 766; 411 NW2d 484 (1987) (a trial court may order child support where a party voluntarily reduces income and the trial court concludes the party has the ability to earn an income); Heilman v Heilman, 95 Mich App 728; 291 NW2d 183 (1980) (a trial court may properly take into consideration a parent’s ability to work and earn money in setting the appropriate child support award). However, in allowing income imputation to a payer whom the court finds to have an unexercised ability to pay, this Court has required specific findings by the trial court. Sword v Sword, supra (in determining a parent’s ability to pay child support, the court must evaluate a number of factors, such as employment history, education and skills, available work opportunities, diligence in trying to find work, the defendant’s personal history, assets, health and physical ability, and availability for work); Rohloff, supra (refers to Sword criteria for determina*199tion of ability to pay child support in voluntary reduction of income case).
The requirement that the trial court evaluate criteria such as those listed in Sword is essential to ensure that any imputation of income is based on an actual ability and likelihood of earning the imputed income. Any other rule would be pure speculation and a clear violation of the requirement that child support be based upon the actual resources of the parents. MCL 552.519(3)(a)(vi); MSA 25.176(19)(3)(a)(vi). Moreover, the manual requires that the decision to impute income be based on the evaluation of “among other equitable factors,” the following eight factors:
1. Prior employment experience;
2. Education level;
3. Physical and mental disabilities;
4. The presence of children of the marriage in the party’s home and its impact on the earnings of the parties;
5. Availability of employment in the local geographical area;
6. The prevailing wage rates in the local geographical area;
7. Special skills and training; or
8. Whether there is any evidence that the party in question is able to earn the imputed income. [Manual at 8.]
The manual also emphasizes that “imputation is not appropriate where ... [a] payee/payer source of income is a means tested income such as Temporary Assistance to Needy Families (tanf), Family Independence Payments (fip) (formerly afdc), Food Stamps, Supplemental Security Income (SSI), etc. ...” Manual at 8.
*200In its decision to allow imputation of income to defendant, despite the fact that her sole source of income was means-tested public assistance, the trial court gave no consideration, except as to defendant’s medical condition, to any of the factors required by Sword or the manual. The Court of Appeals erroneously approved the trial court’s failure to follow the requirements established by the child support formula for any deviation from the formula.
The Legislature has determined that Michigan courts “shall order support in an amount determined by application of the child support formula developed by the state Mend of the court bureau.” MCL 722.717(3); MSA 25.497(3).6 In the absence of circumstances that make a determination “unjust or inappropriate,” the court may not deviate from the formula. Id. The formula provides that imputation is not appropriate where the payee/payer source of income is means-tested income. The trial court in this case made no record of any circumstances, nor have the parties stated any, that would lead to the conclusion that the amount of child support as indicated by the manual is “unjust or inappropriate.”
B
The Court of Appeals, in affirming the trial court’s award of child support in the instant case, largely ignored the mandate of the manual and the state and federal laws that require courts to follow the manual *201when setting the amount of child support. See 222 Mich App 378-379. The Court of Appeals noted the manual’s statement that imputation is “not appropriate where ‘[a] payee/payer source of income is a means tested income such as Aid for Families with Dependent Children, General Assistance, Food Stamps, and Supplemental Security Income.’ ” Id. at 378. The Court of Appeals then stated that “[t]his is consistent with the child support guidelines’ statement that means-tested sources of income ‘should not be considered as income to either parent for the purpose of determining child support.’ ” Id. at 378-379 (emphasis in original). However, the Court of Appeals also found that
although at first glance the language of MCL 400.63; MSA 16.463 and MCL 552.602(c); MSA 25.164(2)(c) may appear to protect defendant from child support obligations because her only income is AFDC, neither statute prohibits imputing wage income to a voluntarily unemployed parent who receives afdc as long as that parent is not required to satisfy the child support order from the afdc grant. [222 Mich App 380 (emphasis in original).]
In fact, the Court of Appeals interpretation is not logically consistent, because imputing fictitious income to a parent receiving afdc would defeat the purpose of ignoring AFDC income in support calculations.
The Court of Appeals found that “[t]he manual contains no substantive right liberating a noncustodial parent who receives afdc from all child support obligations. If this were the case, we would find statutory authorization for this exclusion, but none exists.” Id. at 379. This argument cannot be supported. The manual may not contain this “substantive right,” id., but it *202unambiguously prohibits imputation of income to a parent (custodial or otherwise) who receives afdc. Manual at 10-11. Furthermore, the Legislature statutorily delegated the authority to draft the manual to the friend of the court.7 This delegation was pursuant to federal mandate.8 “An agency’s authority to adopt rules is typically provided for in the statute creating the agency and vesting it with certain powers,” and that “[r]ulemaking authority may also be inferred from other statutory authority granted to an agency.” Bienenfeld, Michigan Administrative Law (2d ed), ch 4, pp 18-19. This Court has said that “what is essential to a valid . . . Michigan ‘rule’ is: a reasonable exer*203cise of legislatively delegated power, pursuant to proper procedure.”9 To say that a rule in the manual needs “statutory authorization” in order to exist is to defeat the purpose of the legislative delegation.
The Court of Appeals then opined that, despite the defendant’s lack of any income other than AFDC and the fact that such income is “absolutely inalienable” under Michigan law, MCL 400.43(1); MSA 16.463(1), the defendant could be assessed child support. The Court of Appeals held that defendant would not be required to pay the assessed child support while her sole source of income was AFDC, but the unpaid weekly child support would accumulate in arrears.10 222 Mich App 380-384. This view cannot overcome the language of 42 USC 667, MCL 722.717(3); MSA 25.497(3), and the manual. These controlling statutes and regulations, read together (as by their terms they must be), prohibit the imputation of income to a parent receiving “means tested income” unless the court determines from the facts of the case that application of the child support formula would be unjust or inappropriate and sets forth in writing or on the record the four pieces of information11 required by MCL 722.717(3); MSA 25.497(3).
*204CONCLUSION
The relevant state and federal statutes require the trial court, in determining the appropriate amount of child support in a particular case, to follow the guidelines set forth by the state agency with the authority to promulgate such guidelines. In Michigan, that agency is the Friend of the Court Bureau, which has published the Michigan Child Support Formula Manual in accordance with state and federal law. The manual clearly and unequivocally prohibits the imputation of income to a payee or payer parent who is receiving means-tested income such as afdc. When a trial court deviates from this formula, it must set forth in writing why following the formula would be “unjust or inappropriate.” This the trial court did not do. The Court of Appeals erred in affirming the trial court’s order.
Therefore, the decision below is reversed, and this case is remanded for a calculation of a support order consistent with this opinion.
Mallett, C.J., and Cavanagh and Kelly, JJ., concurred with Brickley, J.“Means tested public assistance” is used throughout this opinion to refer to federal welfare benefits paid to eligible low-income individuals or families.
MCL 722.717(3); MSA 25.497(3) provides that the court may enter an order of support that varies from that mandated by the guidelines, but only if the court determines from the facts of the case that application of the child support formula would be unjust or inappropriate and sets forth in writing or on the record all of the following:
(a) The support amount determined by application of the child support formula
(b) How the support order deviates from the child support formula.
*192(c) The value of property or other support awarded instead of the payment of child support, if applicable.
(d) The reasons why application of the child support formula would be unjust or inappropriate in the case.
Pursuant to 42 USC 667(b)(2), the State Court Administrative Office Friend of the Court Bureau developed the Michigan Child Support Formula Manual, which provides, in part:
Imputation of income is treating a party as having income or resources that the party does not actually have. This usually occurs in cases where a party voluntarily reduces his/her income.
The determination as to the appropriateness of imputation in a particular case is a judicial one. In all cases in which the Friend of the Court investigation shows voluntary reduction of income or where there is voluntary unexercised ability to earn, the Friend of the Court shall make two recommendations: one is based on actual income and the other is based on actual plus imputed income. The recommendation should also take into account the possible inclusion of a child care recommendation where imputation would make that issue relevant. The recommendation shall include the basis for imputation and the basis of the amount imputed. [Michigan Child Support Formula Manual, tenth rev, p 8 (emphasis in original).]
This legislative mandate is also set forth in MCL 552.519; MSA 25.176(19), which creates the Friend of the Court Bureau as a part of the State Court Administrative Office. The friend of the court is required to “[djevelop and recommend guidelines for conduct, operations, and procedures of the office and its employees,” including a “formula to be used in establishing and modifying a child support amount and health care obligation. The formula shall be based upon the needs of the child and the actual resources of each parent.” MCL 552.519(3)(a)(vi); MSA 25.176(19)(3)(a)(vi).
222 Mich App 378.
The same provision is included in other relevant statutes, such as the divorce act, MCL 552.15(2); MSA 25.95(2); the Family Support Act, MCL 552.452(2); MSA 25.222(2); the emancipation of minors and rights of parents act, MCL 722.3(3); MSA 25.244(3); and the Child Custody Act, MCL 722.27(2); MSA 25.312(7)(2).
In defining the creation, powers and duties of the Friend of the Court Bureau, MCL 552.519; MSA 25.176(19) provides:
(3) The bureau shall do all of the following:
(a) Develop and recommend guidelines for conduct, operations, and procedures of the office and its employees, including, but not limited to, the following:
* * *
(vi) A formula to be used in establishing and modifying a child support amount and health care obligation. The formula shall be based upon the needs of the child and the actual resources of each parent. The formula shall establish a minimum threshold for modification of a child support amount. The formula shall consider the child care and dependent health care coverage costs of each parent.
42 USC 667(a) provides:
Establishment of guidelines; method
Each State, as a condition for having its State plan approved under this part [42 USC 651 et seq.], must establish guidelines for child support award amounts within the State. The guidelines may be established by law or by judicial or administrative action, and shall be reviewed at least once every 4 years to ensure that their application results in the determination of appropriate child support award amounts.
Michigan Farm Bureau v Workmen’s Compensation Bureau, 408 Mich 141, 150; 289 NW2d 699 (1980).
The defendant is now employed and paying the assessed child support. This case is saved from mootness by the fact that substantial arrearage built up during the period when the defendant and her family were subsisting on afdc alone.
(a) The support amount determined by application of the child support formula.
(b) How the support order deviates from the child support formula.
(c) The value of property or other support awarded instead of the payment of child support, if applicable.
*204(d) The reasons why application of the child support formula would be unjust or inappropriate in the case.