Who should own the Google Ads account, the agency or the client?
Short answer
The client. Create the account in your business’s name with an internal administrator. The agency links its manager account for access. Google says a manager account with ownership doesn’t take data ownership or administrative rights away from the client account, and client account users can always unlink a manager.
Google Ads
Agencies usually work through a manager account linked to yours. A linked manager can also be given “ownership”, which grants full administrative access, but Google states that owners “do not take data ownership or administrative rights away from client accounts”, and that client account users “can always unlink a manager” with ownership (Google Ads Help). Keep at least one administrator from your own company on the account. Access levels are Administrative, Standard, Read only, Email only and Billing (Google Ads Help); only give each person the level their job needs.
Meta
Your business portfolio in Meta Business Suite should hold the ad account, Facebook Page, Instagram account and datasets. Meta lets a business give a partner access to assets in its portfolio, or ask a partner to share assets with it (Meta Business Help). Choose the first: assets in your portfolio, the agency added as a partner with access to specific assets.
LinkedIn
Campaign Manager has five roles: billing admin, account manager, campaign manager, creative manager and viewer. “The person who creates the ads account is automatically assigned as the billing admin”, and each ad account must have one (LinkedIn Help). If an agency employee created your account, they are the billing admin until someone reassigns it. Create the account yourself, and give the agency campaign manager access.
Analytics, tags, domains and landing pages
Your company should own the analytics property, the tag manager container, the domain and DNS, and the landing page builder account, with the agency added as a user. Landing pages hosted on an agency’s own subscription disappear when the subscription does.