Set initial value of month = null in the component.ts and
add [(ngModel)]="month" in the select tag of component.html.
//component.ts
month = null;
//component.html
<form #filter="ngForm" (ngSubmit)="filterta(filter)" style="display: flex;">
<select name="month" [(ngModel)]="month" #month required>
<option [ngValue]="null" [disabled]="true" >All</option>
<option value="1">January</option>
</select>
</form>
//angular 1.2.16
<select id="year" ng-model="insData.S_FinYear" name="f_year">
<option value="" disabled selected>Fin Year</option>
<option ng-repeat="YR in F_Year_List" value="{{YR.f_id}}">
{{YR.f_year}}
</option>
</select><i></i>
//nb: not work with ng-options.