State of Minnesota, Respondent, vs. Bounleng Saengchanh, Appellant.

may not be cited except as provided by

Minn. Stat. § 480 A. 08, subd. 3 (1996).

 STATE OF MINNESOTA

 IN COURT OF APPEALS

 C8-97-1373

Kristal Hasskamp,

Respondent,

Ramsey County Child Support

& Collection Office,

Respondent,

vs.

Robert Lundquist,

Appellant.

 Filed February 10, 1998

 Affirmed as modified; motion denied

 Forsberg, Judge**

Ramsey County District Court

File No. FX9750053

Mary Catherine Lauhead, 3985 Clover Avenue, St. Paul, MN 55127-7015 (for respondent Hasskamp)

Susan Gaertner, Ramsey County Attorney, Amy A. Anderson, Assistant County Attorney, 415 Ramsey County Government Center West, 50 West Kellogg Boulevard, St. Paul, MN 55102 (for respondent Ramsey County)

Charles E. Mertensotto, Jill Johnson Sholts, Rowland, Mertensotto & Sholts, P.A., 1100 West Seventh Street, St. Paul, MN 55102 (for appellant)

*Retired judge of the Minnesota Court of Appeals, serving by appointment pursuant to Minn. Const. art. VI, § 10.

Considered and decided by Toussaint, Chief Judge, Crippen, Judge, and Forsberg, Judge.

 U N P U B L I S H E D O P I N I O N

 FORSBERG, Judge

Robert Lundquist appeals a judgment determining his child support obligation and awarding past support in a paternity proceeding. We affirm, but modify the awards to correct the error of the administrative law judge (ALJ) in failing to deduct FICA withholding in determining appellant's net income.

 FACTS

In the underlying administrative proceeding to establish parentage, appellant admitted paternity of two-year-old T.J.H. Respondent Kristal Hasskamp (Hasskamp) is the mother of T.J.H. At the time of T.J.H.'s birth, appellant was married to Marjean Hagerty (Hagerty). Appellant and Hagerty have two children, one of whom was born several months prior to T.J.H. and the other in 1996.

Appellant owns a corporation known as Space Control, and Hagerty owns a corporation known as Storage Engineering. Appellant manages both corporations, which are in the business of independent contracting for millwright work. Appellant testified that Hagerty controls the finances of Storage Engineering and also works part-time as a registered nurse. Appellant stated he receives no compensation from Storage Engineering.

Appellant paid Hasskamp $1,000 per month in child support since T.J.H.'s birth, except for February 1997 when appellant paid $750. Hasskamp testified at the February 12, 1997, hearing that her household expenses were $964 per month, but indicated that these expenses would increase because she had accepted new employment and would have to pay child care expenses.

By order dated March 5, 1997, the ALJ directed appellant to pay $1,099.21 per month as temporary child support. Appellant filed a motion to amend the temporary support order, indicating that Hagerty commenced a dissolution action on March 4, 1997, and that a temporary order was issued in that action on March 10, 1997, directing appellant to pay child support of $865.77 per month and $1,000 per month in spousal maintenance. At a May 19, 1997, hearing, appellant stated that he was still living in the same household with Hagerty and their two children. Appellant did not provide any financial records from Storage Engineering indicating that Hagerty, as sole owner of the company, refused to release the records. Appellant provided no information regarding Hagerty's income or contribution to the household expenses.

In the July 2, 1997, judgment, the ALJ determined that appellant's net annual income from Space Control is $42,589.80. In calculating appellant's total income, the ALJ added other benefits from Space Control, including an annual pension contribution of $8,590, a health plan contribution of $5,280, and $275 per month for the value of a vehicle used by appellant. The ALJ awarded guidelines support of $1,245 per month plus $226.97 per month as appellant's portion of Hasskamp's child care expenses. The ALJ also found that appellant had the ability to reimburse Hasskamp the sum of $26,145 for support during the 24-month period preceding the commencement of the action and awarded Hasskamp a judgment of $5,230, after deducting the $20,915 that appellant already paid.

 D E C I S I O N

 I.

In parentage actions, child support is determined in accordance with Minn. Stat. ch. 518. Minn. Stat. § 257.66, subd. 3 (1996). The district court has broad discretion with respect to the support of the parties' children, and this court will not reverse the district court's decision unless it is clearly erroneous. Rutten v. Rutten, 347 N.W.2d 47, 50 (Minn. 1984).

A determination of net income for the purpose of calculating child support will be affirmed if it has a reasonable basis in fact. Strauch v. Strauch, 401 N.W.2d 444, 447 (Minn. App. 1987). Appellant argues that the ALJ erred in determining his net income available for payment of child support by (1) failing to deduct his tax deductions based on the amounts recommended in the tax tables; (2) failing to deduct FICA withholding from gross income; (3) including the value of health insurance premiums paid by Space Control; and (4) failing to deduct appellant's spousal maintenance and child support obligation in the marital dissolution action.

In calculating federal and state income tax, standard deductions apply and the use of the tax tables is recommended. Minn. Stat. § 518.551, subd. 5(b) (1996). But it is also proper to compute net income by deducting amounts withheld and adding amounts refunded during a particular year. Lenz v. Wergin, 408 N.W.2d 873, 876 (Minn. App. 1987). In this case, the ALJ's finding regarding appellant's state and federal tax liability is not clearly erroneous because it is supported by the tax returns. See Minn. R. Civ. P. 52.01 (findings of fact, whether based on oral or documentary evidence, will not be set aside unless clearly erroneous).

We agree with appellant that the ALJ erred in failing to deduct $3,550.63 for FICA social security taxes and $830.37 for FICA Medicare taxes in determining appellant's net income. Hasskamp and the Ramsey County Child Support Authority (the county) do not dispute that these payments should have been deducted. Instead, Hasskamp and the county contend that the error is harmless because other income was available to appellant from Space Control for payment of child support.

By arguing that Space Control's retained earnings should be considered in determining appellant's income, respondents in effect challenge the ALJ's decision to base child support on appellant's salary from Space Control and the value of certain benefits provided by Space Control. But respondents are precluded from challenging any aspect of the ALJ's order, because they did not file notices of review. This court will not consider a challenge to issues decided adversely to a respondent when the respondent has not filed a notice of review. Kolby v. Northwest Produce Co., Inc., 505 N.W.2d 648, 653 (Minn. App. 1993). The ALJ's failure to deduct the FICA withholding is not de minimus and requires modification of the award as directed below.

Appellant contends that the ALJ erred by including the value of health insurance premiums paid by Space Control in determining his income. Whether a source of funds is income for purposes of determining a person's child support obligation is a question of law. Sherburne County Soc. Servs. v. Riedle, 481 N.W.2d 111, 112 (Minn. App. 1992). Net income for purposes of determining child support includes "in-kind payments received by the obligor in the course of employment, self-employment, or operation of a business if the payments reduce the obligor's living expenses." Minn. Stat. § 518.551, subd. 5(b)(1).

Appellant contends that employer-paid health insurance premiums should not be considered income because the statute allows deduction of the costs of dependent health insurance coverage, individual or group health/hospitalization coverage, or an amount for actual medical expenses. Minn. Stat. § 518.551, subd. 5(b). But the deduction is available only for the obligor and any child covered by the child support order. Borcherding v. Borcherding, 566 N.W.2d 90, 93 (Minn. App. 1997). In this case, the record does not show what proportion of the employer-paid benefits would be deductible by appellant if he paid them himself. Because appellant failed to meet his burden to show what percentage of the employer-paid premiums should be excluded consistent with the statute, the ALJ did not err in including the entire value of the benefits in determining appellant's income.

Finally, appellant argues that it was an abuse of discretion for the ALJ to refuse to consider his spousal maintenance and child support obligations in the marital dissolution action in calculating child support for T.J.H. If the obligor is currently paying the prior support, the obligor is entitled to have the amount deducted from gross income in determining the new obligation under the child support guidelines. Minn. Stat. § 518.551, subd. 5(b); Wollschlager v. Wollschlager, 395 N.W.2d 135, 136 (Minn. App. 1986). But because appellant's support obligation for T.J.H. predated the temporary order for support and maintenance in the marital dissolution action, the ALJ did not err in failing to deduct appellant's family support obligation in the marital dissolution action from his income in determining support for T.J.H.

The district court may consider the obligor's current family obligations in determining the obligor's available resources to pay child support. Hayes v. Hayes, 473 N.W.2d 364, 365 (Minn. App. 1991). In determining whether there should be deviation from the guidelines to consider the needs of subsequent children, the obligor's reasonable expenses must be reduced as appropriate to take into account contributions to those costs by others who share the obligor's current household. Bock v. Bock, 506 N.W.2d 321, 325 (Minn. App. 1993). In this case, the ALJ properly refused to consider appellant's current family obligations because appellant is still living in the same household with his family, which receives the benefit of his support payments, and because appellant failed to provide any information regarding Hagerty's contributions to the household expenses.

In summary, we affirm the determination of appellant's income and child support obligation, except for the failure to deduct FICA taxes totaling $4,381, equal to $365 per month. Subtraction of this amount from the net income determined by the ALJ of $4,979.98 per month results in a corrected net monthly income of $4,614.98. Appellant's child support obligation is modified to $1,153.75 per month, the guidelines award based on appellant's corrected net monthly income.

Appellant contends that the erroneous determination of his net monthly income requires reversal of his obligation to pay $226.97 per month for his portion of child care expenses for T.J.H. The district court is required to allocate the costs of child care to each parent in proportion to each parent's net income after the transfer of child support and spousal maintenance, unless the allocation would be substantially unfair to either parent. Minn. Stat. § 518.551, subd. 5(b). Because our correction of appellant's net income has only a minimal effect on the allocation of child care expenses, we decline to modify appellant's child care expense obligation. See Minn. R. Civ. P. 61 (court must disregard any error that does not affect the substantial right of the parties).

 II.

A district court's determination of past support is reviewed under an abuse of discretion standard. Nash v. Allen, 392 N.W.2d 244, 249 (Minn. App. 1986), review denied (Minn. Oct. 22, 1986). The court shall limit the parent's liability for past support to the proportion of the expenses that were incurred in the two years immediately preceding the commencement of the action that the court deems just. Minn. Stat. § 257.66, subd. 4 (1996). In this case, the ALJ determined appellant's support obligation by multiplying the monthly support award of $1,245 by 21 months, the period from April 1995 when T.J.H. was born to January 31, 1997, when the paternity action was commenced. The ALJ found that appellant owes a net past support award of $5,230, after deducting appellant's voluntary contributions of $20,915 from the total award of $26,145.

Appellant argues that the $5,230 award is an abuse of discretion because of the erroneous calculation of his net monthly income and because of the ALJ's failure to consider Hasskamp's resources, T.J.H.'s past expenses, and appellant's obligation to support his other children.

In 1995, Minn. Stat. § 257.66, subd. 4, was amended to include a provision that in determining the amount of the parent's liability for past support, the court may deviate downward from the guidelines if: (1) the child for whom child support is sought is more than five years old and the obligor discovered or was informed of the existence of the parent and child relationship within one year of commencement of the action seeking support; (2) the obligor is a custodian for or pays support for other children; and (3) the obligor's family income is less than 175% of the federal poverty level. See 1995 Minn. Laws ch. 257, art. I, § 18. By specifying the circumstances under which the district court may deviate downward from the guidelines in determining the amount of the parent's liability for past support, the amendment implies that the amount of past support ordinarily should be determined pursuant to the guidelines. The criteria set out in the statute for a downward deviation are not met here because T.J.H. is less than five years old and appellant's family income exceeds 175% of the federal poverty level. The ALJ correctly determined that appellant's guidelines support obligation should be used in determining his obligation to pay past child support.

Because the ALJ overstated appellant's guidelines support obligation by failing to deduct FICA withholding, we will modify the past support award, consistent with our modification of appellant's ongoing child support obligation. Appellant's total past support obligation is $24,228.75, or 21 times the corrected child support obligation of $1,153.75 per month. Appellant's net past child support obligation is modified to $3,313.75.

 III.

Appellant moves to strike the responsive brief submitted by the county on the grounds that the county was not entitled to file a brief and that the brief refers to new matters for the first time on appeal. Because Hasskamp and the county are separate parties, the county was entitled to file its own responsive brief. See Minn. Stat. § 518.255 (1996) (no attorney-client relationship exists between the attorney representing the public authority and the child support recipient). We decline to strike the county's brief, but we have not considered the references in the brief to documents outside the record for this appeal.

  Affirmed as modified; motion to strike denied.