A D.O. (Demi-Official) letter is written in the first person and personal tone — 'I shall be grateful...' — and is used to seek personal attention on a matter. It is typically between officers within two levels of seniority. A regular letter is in the third person — 'I am directed...' — and is more formal.
Source: CSMOP Para 28
What is the sequence of certification?
Why must Ministerial oral orders be confirmed in writing even when they follow the rules?
Does this rule apply to social media accounts of Ministries as well?
Can a nationalized bank other than SBI act as the 'Bank' under GAR?
Who is responsible for keeping the residential address list of Section staff?
This answer is for informational purposes only and does not constitute legal advice. Always refer to the original rules and consult competent authorities for official interpretation.