application/modules/payment_method_interkassa/assets/form.tpl
<form id="paidForm" name="payment" method="post" action="https://sci.interkassa.com/" accept-charset="UTF-8">
<input type="hidden" name="ik_co_id" value="{echo $data['ik_co_id']}" /> <!-- ид кассы -->
<input type="hidden" name="ik_pm_no" value="{echo $data['ik_pm_no']}" /> <!-- ид -->
<input type="hidden" name="ik_am" value="{echo $data['ik_am']}" /><!-- Сумма платежа -->
<input type="hidden" name="ik_desc" value="{echo $data['ik_desc']}" /><!-- Описание -->
<input type="hidden" name="ik_cur" value="{echo $data['ik_cur']}" /><!-- Валюта -->
<input type="hidden" name="ik_suc_u" value="{echo $data['ik_suc_u']}" /><!-- ссылка success -->
<input type="hidden" name="ik_pnd_u" value="{echo $data['ik_pnd_u']}" /><!-- ожидания -->
<input type="hidden" name="ik_fal_u" value="{echo $data['ik_fal_u']}" /><!-- ошибка -->
<input type="hidden" name="ik_sign" value="{echo $signature}" /><!-- ошибка -->
<div class='btn-cart btn-cart-p'>
<input type='submit' value='{lang('Оплатить','payment_method_interkassa')}'>
</div>
</form>