But I now have it working thank you so much. Incase anyone else in NZ wants to know I edit it in manager I put
{% assign C11 = totalPurchases[GST_15] | plus: totalImports %}
{% assign C12 = taxOnPurchases[GST_15] | default: 0.00Format: 0.00 %}
{% assign C13 = GSTOnImports| default: 0.00Format: 0.00 %}
{% if C12 %}
{% assign C14 = taxOnPurchases[GST_15] | plus: gstOnImports %}
{% else%}
{% assign C14 = C13 Format: 0.00 %}
{% endif %}