In case that the Tax Liable field of the SalesInvoiceHeader is a boolean, you could do as follows in the onpredataitem of the report.
Tax Liable is boolean
SalesInvoiceHeader.SETRANGE("Tax Liable",TaxFilter);
In case that Tax Liable is option
IF TaxFilter THEN
"SalesInvoiceHeader".SETRANGE("Tax Liable",SalesInvoiceHeader."Tax Liable"::Yes)
ELSE
"SalesInvoiceHeader".SETRANGE("Tax Liable",SalesInvoiceHeader."Tax Liable"::No);
You should consider filtering out the records that you do not want to work with (the ones you wanna skip) instead of skipping them. Not retrieving them is always more efficient than reading them and doing nothing with them after :-)