Try following way
<?xml version="1.0"?>
<config xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="urn:magento:module:Magento_Config:etc/system_file.xsd">
<system>
<section id="general" translate="label" type="text" sortOrder="10" showInDefault="1" showInWebsite="1" showInStore="1">
<group id="store_information" translate="label" type="text" sortOrder="100" showInDefault="1" showInWebsite="1" showInStore="1">
<field id="merchant_vat_number1" translate="label" type="text" sortOrder="62" showInDefault="1" showInWebsite="1" showInStore="0">
<label>VAT Number1</label>
<can_be_empty>1</can_be_empty>
</field>
</group>
</section>
</system>
</config>
If your module has system.xml then you need to add <section> only otherwise whole text inside system.xml