ORS § 90 § 90.220

(1) A landlord and a tenant may include in a rental agreement terms and conditions not prohibited by this chapter or other rule of law including rent, term of the agreement and other provisions governing the rights and obligations of the parties.

(2) The terms of a fixed term tenancy, including the amount of rent, may not be unilaterally amended by the landlord or tenant.

(3) The landlord shall provide the tenant with a copy of any written rental agreement and all amendments and additions thereto.

(4) Except as provided in this subsection, the rental agreement must include a disclosure of the smoking policy for the premises that complies with ORS 479.305. A disclosure of smoking policy is not required in a rental agreement subject to ORS 90.505 to 90.850 for space in a facility as defined in ORS 90.100.

(5) Notwithstanding ORS 90.245 (1), the parties to a rental agreement to which ORS 90.100 to 90.465 apply may include in the rental agreement a provision for informal dispute resolution.

(6) In absence of agreement, the tenant shall pay as rent the fair rental value for the use and occupancy of the dwelling unit.

(7) Except as otherwise provided by this chapter:

(a) Rent is payable without demand or notice at the time and place agreed upon by the parties. Unless otherwise agreed, rent is payable at the dwelling unit, periodic rent is payable at the beginning of any term of one month or less and otherwise in equal monthly or weekly installments at the beginning of each month or week, depending on whether the tenancy is month-to-month or week-to-week. Rent may not be considered to be due prior to the first day of each rental period. Rent increases must comply with the provisions of ORS 90.323.

(b) If a rental agreement does not create a week-to-week tenancy, as defined in ORS 90.100, or a fixed term tenancy, the tenancy shall be a month-to-month tenancy.

(8) Except as provided by ORS 90.427 (11), a tenant is responsible for payment of rent until the earlier of:

(a) The date that a notice terminating the tenancy expires;

(b) The date that the tenancy terminates by its own terms;

(c) The date that the tenancy terminates by surrender;

(d) The date that the tenancy terminates as a result of the landlord failing to use reasonable efforts to rent the dwelling unit to a new tenant as provided under ORS 90.410 (3);

(e) The date when a new tenancy with a new tenant begins;

(f) Thirty days after delivery of possession without prior notice of termination of a month-to-month tenancy; or

(g) Ten days after delivery of possession without prior notice of termination of a week-to-week tenancy.

(9)(a) Notwithstanding a provision in a rental agreement regarding the order of application of tenant payments, a landlord shall apply tenant payments in the following order:

(A) Outstanding rent from prior rental periods;

(B) Rent for the current rental period;

(C) Utility or service charges;

(D) Late rent payment charges; and

(E) Fees or charges owed by the tenant under ORS 90.302 or other fees or charges related to damage claims or other claims against the tenant.

(b) This subsection does not apply to rental agreements subject to ORS 90.505 to 90.850.