The most common way multinational corporations abuse or avoid tax is by shifting the profits they make out of the countries where they genuinely do business and into tax havens. This allows the corporation to under report its profit it made in the country where it does business, and so pay less or no tax, and to not pay tax on the profit shifted out of the country.
For example, a multinational corporation can setup a shell company in Ireland and make the shell company the owner of its branding. The shell company then charges the multinational corporation’s other companies (ie the ones that actually sell good and services in other countries) expensive royalty fees to use the branding. This creates costs for the companies that they must pay into the tax haven, effectively driving down their profits and “shifting” them into the tax haven.