Did you try by adjusting the top margin of your div containing customer address?

For eg:

<template id="report.new_layout_header">
		<div class="header">
				
		        <div class="row">
		            <div class="col-xs-12">
		                <div style="border-bottom: 1px solid black;"></div>
		            </div>
		        </div>
		        <div class="row mt8 mb8">
		            <div class="col-xs-5">
		                <div t-field="company.partner_id" 
		                    t-field-options='{"widget": "contact", "fields": ["address", "name"], "no_marker": true}'
		                    style="border:1px solid #000000;"/>
		            </div>
	        	</div>
					
		</div>
</template>