To adjust the invoice template to the letterhead, you need to set the invoice margins accordingly. 

Below you can find some hints on how to make such a modification and, on the basis of test printouts, adjust the margins to your letterhead. 

To make such modifications, go to Settings > Account settings > (menu on the left ) select Print settings and on this page, at the bottom, in the field Customize print with CSS, type the following code:

Then you need to change the numerical values ​​of the margins respectively: top, right, bottom and left to match the letterhead (it is important not to remove any other letters or characters from the above code). Note! To make sure that the CSS code will work correctly, please rewrite it manually, do not copy it. The above code does not work in the Blue template.  For the Gray template, use the following instruction: 1. Create a new template based on the gray template 2. Go to the template edition  3. Under @media all { in the second line of code, paste:

.invoice_outline {
min-height: 20cm !important;
padding-top: 4cm !important;
}

.main_inv_table:nth-of-type(n+2) {
margin-top: 4cm !important;
}

@media print {
#description_footer {
display: block !important;
padding-left: 0 !important;
padding-right: 0 !important;
}
}

For more information, please see this post.