You can hand accessibility off to the client when you’re done – if you want.
Content creators are often working within a CMS (e.g., WordPress, Squarespace) or eCommerce platform (e.g., Magento, Shopify). When the platform is configured correctly, it is very easy for them to create accessible content without your help.
You have already set them up with the WCAG-compliant brand colors, fonts, and page layouts within the CMS or eCommerce platform. That leaves very little left for the person creating the content and can be condensed into a short checklist for them to review before publishing.
If you have partnered with an accessibility firm, like Level Access, you can include regular accessibility monitoring for your client as part of your website maintenance package.