It is too late in the month to terminate this tenancy on a 20-day notice. The soonest you could have them out on a 20-day would be August 31. Giving that notice properly would definitely be the surest way to end this tenancy though.
You can do a 3-day if they owe you anything. Don't put any values on the 3-day other than rent. Do your level best to make the 3-day accurate.
You could do a 3-day vacate for gang/drug/unlawful activity but the problem is you have to identify where the information came from, otherwise it is hearsay, and your neighbors may not want a criminal to know where the information you have came from. Surely you can see the problem with that.
If you do a 3-day vacate for unlawful activity, you are setting up a factual battle and that requires a trial, and that can cost a fortune. Better to assert the properly timed 20-day, or a 3-day pay or vacate as the basis for your eviction action.
The best outcome for you is to get your property back in the least amount of time so you can find a new tenant who will pay the rent on time. People who forget to pay their rent are seldom worth chasing after for payment because they don't have any money.
In Thurston County, contact John Woodring's office. They are very good at this.
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