I deduct Washington state sales tax every year. I have heard that this deduction will not be allowed in the 2018 tax year. Can someone let me know if this is a fact?

The new law does not eliminate the deduction for state sales tax.  Instead, it limits the deductible amount.  Under the new plan, taxpayers who are able to itemize will be able to deduct their state individual income, sales and property taxes up to a limit of $10,000 in total.

Remember that  many taxpayers who are used to itemizing likely won't be doing so this year (2018) because of the big increase in the standard deduction.