Can a commercial landlord demand back payment for a rent increase + Holdover rent in Washington State without prior notice?

The commercial rental agreements often have an automatic increase in rent if the tenant holdovers. If you stay after your lease expired without making arrangements with your landlord, you hold over. Your rental agreement is your notice. That the landlord did not tell you right away about the rent increase is probably not detrimental to the landlord. You, presumably, can read the lease as well as the landlord. Your lease likely also provides that you are to pay the rent, whatever it may be, without the landlord having to tell you how much to pay. That is, you are supposed to pay 125% of the old rent without the landlord having to send you any invoice. Unless the 3% increase is also in your lease, you are not required to pay a rent increase until you have been given notice. No one here has seen your lease. You apparently do not know what is in your lease either. So, what you likely should do is review the lease and other facts with your attorney to see what your legal options are. The holdover clause, with its huge rent increase, is often used to move along tenants the landlord no longer wants. If you are in good terms with the landlord, you likely can convince the landlord to just accept the 3% increase (which likely is much better than the 25% increase).