What legal basis would I rely on to send marketing material to customers under the GDPR? Please include soft opt-in as well.

Under the GDPR, there are several legal bases you can rely on to send marketing material to customers, depending on the specific circumstances. Consent: This is the most common legal basis for sending marketing material. To use consent, you must obtain explicit, freely given, and specific consent from the individual to receive marketing material. This consent must be obtained through a clear and affirmative action (such as checking a box) and cannot be inferred from silence, pre-ticked boxes, or inactivity. Legitimate Interest: You may also rely on legitimate interest as a legal basis for sending marketing material. This applies if you have a legitimate interest in sending the material and your interests do not override the individual's rights and freedoms. You should carry out a legitimate interest assessment to ensure that you have a valid legitimate interest. Soft Opt-in: This is a specific exemption from the GDPR's consent requirement that applies in some circumstances. The soft opt-in applies when you have obtained an individual's contact details during the course of a sale or negotiations of a sale of a product or service, and you are sending marketing material about similar products or services. In this case, you can send marketing material without obtaining explicit consent, but you must offer the individual the opportunity to opt-out of future marketing material. It's worth noting that the soft opt-in only applies to existing customers or individuals who have expressed an interest in your products or services. You cannot use it to send marketing material to individuals who have not had any previous contact with your business. Regardless of the legal basis used, you must provide clear information to individuals about how their data will be used and give them the option to opt-out of receiving marketing material at any time.