Explain the provisions relating to rectification of errors apparent on the face of record under section 161.

Section 161 of the CGST Act, 2017 lays down that any authority, who has passed or issued any decision or order or notice or certificate or any other document, may rectify any error which is apparent on the face of record in such decision or order or notice or certificate or any other document, either on its own motion or where such error is brought to its notice by any GST officer or by the affected person within a period of three months from the date of issue of such decision or order or notice or certificate or any other document, as the case may be. However, no such rectification shall be made after a period of six months from the date of issue of such decision or order or notice or certificate or any other document. Further, the said period of six months shall not apply in such cases where the rectification is purely in the nature of correction of a clerical or arithmetical error, arising from any accidental slip or omission. Principles of natural justice should be followed by the authority carrying out such rectification, if it adversely affects any person.