IRS Definition of Terms – you may find helpful  (Part I)

Julian Date — The numeric day of the year that the return or document was numbered for processing. (For example: January 15 +MC 015). The sixth, seventh and eighth digits of the DLN represent the Julian Date. Note: If the DLN is IDRS generated, this date will be incremented by 400 so January 15 would be shown as 415. 

Claim—FORMAL — A request prepared by or for the taxpayer submitted on Form 1040X, 843, and 1120X to reduce liabilities previously assessed. It can also be an amended return. INFORMAL — A letter or other document, not on Form 843, but prepared and signed by the taxpayer, requesting changes to obtain correct and accurate reflection of his/her tax liability.

Installment Agreement Record — A record in IDRS containing installment agreement information.

Unpostables (UP) – Data that cannot be posted (updated) to a master file due to an unprocessable condition such as an incorrect TIN, date or transaction code.

(IRS Document 6209, TTT 8/3/21 & 8/10/21)