535.2  Rate of interest.
  1.  Except as provided in subsection 2 hereof, the rate of interest shall be five cents on the hundred by the year in the following cases, unless the parties shall agree in writing for the payment of interest at a rate not exceeding the rate permitted by subsection 3:
  a.  Money due by express contract.
  b.  Money after the same becomes due.
  c.  Money loaned.
  d.  Money received to the use of another and retained beyond a reasonable time, without the owner’s consent, express or implied.
  e.  Money due on the settlement of accounts from the day the balance is ascertained.
  f.  Money due upon open accounts after six months from the date of the last item.
  g.  Money due, or to become due, where there is a contract to pay interest, and no rate is stipulated.
  2.  a.  The following persons may agree in writing to pay any rate of interest, and a person so agreeing in writing shall not plead or interpose the claim or defense of usury in any action or proceeding, and the person agreeing to receive the interest is not subject to any penalty or forfeiture for agreeing to receive or for receiving the interest:
  (1)  A person borrowing money for the purpose of acquiring real property or refinancing a contract for deed.
  (2)  A person borrowing money or obtaining credit in an amount which exceeds twenty-five thousand dollars, exclusive of interest, for the purpose of constructing improvements on real property, whether or not the real property is owned by the person.
  (3)  A vendee under a contract for deed to real property.
  (4)  A domestic or foreign corporation, and a real estate investment trust as defined in section 856 of the Internal Revenue Code, and a person purchasing securities as defined in chapter 502 on credit from a broker or dealer registered or licensed under chapter 502 or under the Securities Exchange Act of 1934, 15 U.S.C., ch. 78A, as amended.
  (5)  A person borrowing money or obtaining credit for business or agricultural purposes, or a person borrowing money or obtaining credit in an amount which exceeds twenty-five thousand dollars for personal, family, or household purposes. As used in this paragraph, “agricultural purpose” means as defined in section 535.13, and “business purpose” includes but is not limited to a commercial, service, or industrial enterprise carried on for profit and an investment activity.
  b.  In determining exemptions under this subsection, the rules of construction stated in this paragraph apply:
  (1)  The purpose for which money is borrowed is the purpose to which a majority of the loan proceeds are applied or are designated in the agreement to be applied.
  (2)  Loan proceeds used to refinance or pay a prior loan owed by the same borrower are applied for the same purposes and in the same proportion as the original principal of the loan that is refinanced or paid.
  (3)  If the lender releases the original borrower from all personal liability with respect to the loan, loan proceeds used to pay a prior loan by a different borrower are applied for the new borrower’s purposes in agreeing to pay the prior loan.
  (4)  If the lender releases the original borrower from all personal liability with respect to the loan, the assumption of a loan by a new borrower is treated as if the new borrower had obtained a new loan and had used all of the proceeds to pay the loan assumed.
  (5)  This paragraph does not modify or limit section 535.8, subsection 2, paragraph “c” or “e”.
  (6)  With respect to any transaction referred to in paragraph “a” of this subsection, this subsection supersedes any interest-rate or finance-charge limitations contained in the Code, including but not limited to this chapter and chapters 321, 322, 524, 533, 534, 536A, and 537.
  3.  a.  (1)  The maximum lawful rate of interest which may be provided for in any written agreement for the payment of interest entered into during any calendar month commencing on or after April 13, 1979, shall be two percentage points above the monthly average ten-year constant maturity interest rate of United States government notes and bonds as published by the board of governors of the federal reserve system for the calendar month second preceding the month during which the maximum rate based thereon will be effective, rounded to the nearest one-fourth of one percent per year.
  (2)  On or before the twentieth day of each month the superintendent of banking shall determine the maximum lawful rate of interest for the following calendar month as prescribed herein, and shall cause this rate to be published, as a notice in the Iowa administrative bulletin or as a legal notice in a newspaper of general circulation published in Polk county, prior to the first day of the following calendar month. This maximum lawful rate of interest shall be effective on the first day of the calendar month following publication. The determination of the maximum lawful rate of interest by the superintendent of banking shall be exempt from the provisions of chapter 17A.
  b.  Any rate of interest specified in any written agreement providing for the payment of interest shall, if such rate was lawful at the time the agreement was made, remain lawful during the entire term of the agreement, including any extensions or renewals thereof, for all money due or to become due thereunder including future advances, if any.
  c.  Any written agreement for the payment of interest made pursuant to a prior written agreement by a lender to lend money in the future, either to the other party to such prior written agreement or a third party beneficiary of such prior agreement, may provide for payment of interest at the lawful rate of interest at the time of the execution of the prior agreement regardless of the time at which the subsequent agreement is executed.
  d.  Any contract, note or other written agreement providing for the payment of a rate of interest permitted by this subsection which contains any provisions providing for an increase in the rate of interest prescribed therein shall, if such increase could be to a rate which would have been unlawful at the time the agreement was made, also provide for a reduction in the rate of interest prescribed therein, to be determined in the same manner and with the same frequency as any increase so provided for.
  4.  a.  Notwithstanding the provisions of subsection 3, with respect to any agreement which was executed prior to August 3, 1978, and which contained a provision for the adjustment of the rate of interest specified in that agreement, the maximum lawful rate of interest which may be imposed under that agreement shall be nine cents on the hundred by the year, and any excess charge shall be a violation of section 535.4.
  b.  Notwithstanding the limitation contained in paragraph “a” of this subsection, with respect to a written agreement for the repayment of money loaned, which was executed prior to August 3, 1978 and which provided for the payment of over fifty percent of the initial principal amount of the loan as a single payment due at the end of the term of the agreement, the interest rate may be adjusted after June 3, 1980 according to the terms of the agreement to any rate of interest permitted by the laws of this state as of the date an adjustment in interest is to be made. This paragraph does not authorize adjustment of interest in any manner other than that expressly permitted by the terms of the written agreement, and nothing contained in this paragraph authorizes the collection of additional interest with respect to any portion of a loan which was repaid prior to the effective date of an interest rate adjustment.
  c.  Notwithstanding paragraph “a”, when a written agreement providing for the repayment of money loaned, and requiring the payment of over fifty percent of the initial principal amount of the loan as a single payment due at the end of the term of the agreement is extended, renewed, or otherwise amended by the parties on or after August 3, 1978, the parties may agree to the payment of interest from the effective date of the extension, renewal, or amendment, at a rate and in a manner that is lawful for a new agreement made on that date.
  5.  This section shall not apply to any loan which is subject to the provisions of section 636.46.
  6.  a.  Notwithstanding the provisions of 1980 Iowa Acts, chapter 1156, with respect to any agreement which was executed on or after August 3, 1978, and prior to July 1, 1979, and which contained a provision for the adjustment of the rate of interest specified in the agreement, the maximum lawful rate of interest which may be imposed under that agreement shall be that rate which is two and one-half percentage points above the rate initially to be paid under the agreement, provided that the greatest interest rate adjustment which may be made at any one time shall be one-half of one percent and an interest rate adjustment may not be made until at least one year has passed since the last interest rate adjustment, and any excess charge shall be a violation of section 535.4.
  b.  Notwithstanding the limitation contained in paragraph “a” of this subsection, with respect to a written agreement for the repayment of money loaned which was executed on or after August 3, 1978, and prior to July 1, 1979, and which provided for the payment of over fifty percent of the initial principal amount of the loan as a single payment due at the end of the term of the agreement, the interest rate may be adjusted after June 3, 1980, according to the terms of the agreement to any rate of interest permitted by the laws of this state as of the date an adjustment in interest is to be made. This paragraph does not authorize adjustment of interest in any manner other than that expressly permitted by the terms of the written agreement, and nothing contained in this paragraph authorizes the collection of additional interest with respect to any portion of a loan which was repaid prior to the effective date of an interest rate adjustment.
  7.  This section does not apply to a charge imposed for late payment of rent. However, in the case of a residential lease, a late payment fee shall not exceed ten dollars a day or forty dollars per month.
[C51, §945; R60, §1787; C73, §2077; C97, §3038; C24, 27, 31, 35, 39, §9404; C46, 50, 54, 58, 62, 66, 71, 73, 75, 77, 79, S79, C81, §535.2; 82 Acts, ch 1153, §4, 5]
93 Acts, ch 154, §5; 95 Acts, ch 125, §1; 2011 Acts, ch 25, §65
Life insurance policy loans; see §511.36 
Subsection 3, paragraph a, unnumbered paragraphs 1 and 2 editorially designated as subparagraphs (1) and (2)
Subsection 6, paragraph a amended