This opinion will be unpublished and may not be cited except as provided by Minn. Stat. § 480A.08, subd. 3 (1994). STATE OF MINNESOTA IN COURT OF APPEALS C3-96-430 In Re the Marriage of: J.C.P., petitioner, Respondent, vs. J.E.P., Appellant. Filed August 13, 1996 Affirmed Schumacher, Judge Washington County District Court File No. F6882381 Paul W. Rogosheske, Thuet, Pugh & Rogosheske, Ltd., 833 Southview Boulevard, South St. Paul, MN 55075 (for Respondent) Hugh W. McLeod III, 1130 Pleasant Circle, Arden Hills, MN 55112 (for Appellant) Considered and decided by Short, Presiding Judge, Schumacher, Judge, and Holtan, Judge.* U N P U B L I S H E D O P I N I O N SCHUMACHER, Judge Appellant J.E.P. (mother) claims that the district court erred in denying her request for a cost-of-living adjustment (COLA) in respondent J.C.P.'s (father) maintenance and support obligations and in refusing to compel father to pay attorney fees. We affirm. FACTS The 1990 amended judgment dissolving the parties' marriage awarded mother custody, support, maintenance, a COLA for maintenance and support, and attorney fees. In March 1995, the county sent father a notice that a COLA would increase maintenance and support effective in May 1995. Father objected and the district court stayed the increase pending a hearing. The county later withdrew its support for the COLA and mother moved for both a COLA and to compel father to pay allegedly unpaid attorney fees. After a hearing, the district court allowed father to file an affidavit addressing attorney fees. Father filed an affidavit concerning attorney fees and a copy of a 1992 affidavit by mother in which she stated that the fees had been paid. The district court denied mother's motions, finding that father's income had substantially decreased between 1993 and 1994 and that mother had presented insufficient evidence on her claim of unpaid attorney fees. Mother appeals. D E C I S I O N 1. If an obligor shows an "insufficient cost of living or other increase in income," the district court "may" order that all or part of a COLA increase not take effect. Minn. Stat. § 518.641, subd. 3 (1994). If the obligor fails to show an insufficient increase in income, a COLA "shall" take effect. Id. The district court found that father's income substantially decreased from 1993 to 1994 and refused to impose a COLA. Mother claims that the district court should have averaged father's income over several years to determine whether father's income had increased sufficiently to allow a COLA. Mother cites no cases requiring income averaging in the COLA context, the cases mother does cite to support her argument are distinguishable, and father's income is currently less than it has been at any time since the dissolution. On this record, we cannot say that it was an abuse of the district court's discretion to refuse to impose the COLA. See McClenahan v. Warner, 461 N.W.2d 509, 511 (Minn. App. 1990) (obligor has burden of showing why all or part of COLA should not be ordered and the district court's discretion is limited to granting or denying COLA). 2. Mother claims that the district court's findings are inadequate to support the denial of a COLA. See Mower County Human Servs. v. Hueman, 543 N.W.2d 682, 685 n.1 (Minn. App. 1996) (findings required if district court waives COLA). On this record, the district court's findings concerning the decrease in father's income are not clearly erroneous and support the denial of a COLA. See Minn. R. Civ. P. 52.01 (findings of fact not set aside unless clearly erroneous); Hueman, 543 N.W.2d at 685 (district court abused its discretion in imposing support COLA where obligor's only source of income lacked COLA). 3. The amended judgment requires father to pay mother's former attorneys $25,000 in installments. Mother claims that because father did not prove that he made the final installment payment, it should be presumed that he did not make that payment. The parties dispute the creation and impact of a "presumption" under Minn. R. Evid. 301. "A presumption is an assumption of fact required by law once certain underlying or basic facts are established." 11 Peter N. Thompson, Minnesota Practice § 301.01 at 94 (1992) (footnote omitted). Mother cites no authority requiring the assumption that father did not make his final payment. Even if a presumption that father did not make the last payment could arise, a presumption dictates a decision only where there is an entire lack of competent evidence to the contrary and the very moment substantial countervailing evidence appears from any source it ceases to have any function and vanishes completely from the cause as if it had never existed. Kath v. Kath, 238 Minn. 120, 124, 55 N.W.2d 691, 693-94 (1952). Father entered both his affidavit indicating that he believed the payment to have been made and a copy of mother's 1992 affidavit in which she states that father had paid or assigned $25,000 to her former attorneys. Any presumption that father did not make the final payment to mother's former attorneys ceased to have effect when father filed these documents. We defer to the district court's resolution of the fact question raised by the parties' affidavits. See Straus v. Straus, 254 Minn. 234, 235, 94 N.W.2d 679, 680 (1959) (appellate courts defer to district court resolution of fact issues presented by conflicting affidavits). Affirmed. * Retired judge of the district court, serving as judge of the Minnesota Court of Appeals by appointment pursuant to Minn. Const. art. VI, § 10.