Product certification Scheme which is popularly known as the "SLS Marks Scheme", is a scheme that gives a third party guarantee on quality of a product. This scheme enables the SLSI to grant permits to local as well as overseas manufacturers producing goods conforming to Sri Lanka Standards to mark the "SLS" mark on their products. Sri Lanka Standards Institution Act No.6 of 1984, and the regulations made there under empower the Sri Lanka Standards Institution to issue such permits to manufacturers.

The Product Certification Scheme is essentially voluntary in nature. However, SLS Mark has been made compulsary through the Directions issued under the Consumer Protection Act No. 1 of 1979 and Consumer Affairs Authority Act No. 9 of 2003.

The Certification Mark on a commodity or product signifies that the commodity or product is consistently manufactured in accordance with the relevant Sri Lanka Standard Specification and could be purchased with a reasonable assurance of quality. Compliance with the requirements of the specification is assured through regular monitoring of the quality assurance system through audits carried out by qualified Auditors of the Institution and product testing.

The general policy of the Institution is to administer the Certification Marks Scheme in such a manner that the responsibility of compliance with the relevant standard lies with the manufacturer. To secure this, a suitable quality assurance system consistent with the guidelines prescribed by the Institution should be adopted by each Permit Holder. He is responsible for the documentation and the implementation of the quality system and the continued effectiveness of the quality system will be verified by the qualified officers of the Institution at regular intervals.