Legal practice question -- Oregon

Is it an acceptable legal practice in Oregon to post a notice to Homeowners in a HOA that their semi annual assessments are due Dec 1 and July 1 and to state that if they do not pay their fees on time they will be assessed late fees - even though statements and notices of late payments are not sent to homeowners by the property management company managing their accounts?

Your HOA by-laws and charter etc. almost certainly spell out how notices are required to be given. I have never seen ones that did not.

So check that as a first step.