subjunctive mood
The form that marks a condition contrary to fact, or a demand.
For a present condition contrary to fact, use were: If I were ready, I would file. For a demand, recommendation, or necessity after that, use the base form of the verb: The rule requires that he file the brief. Do not use If I was ready for a condition that is not true.
Examples
UseIf she were here, she would sign.
AvoidIf she was here, she would sign. (If you mean she is not here.)
UseThe rule requires that he file the brief.
AvoidThe rule requires that he files the brief.