--- description: Reservations are system documents that show a requirement for a certain amount of good for production, cost center and any other need. Reservations are important in planning/MRP/ATP as the system res title: Reservation of Inventory in SAP MB21, MB1A, MBST, MB22 image: https://www.guru99.com/images/reservation-of-inventory-in-sap-mm.png --- [Skip to content](#main) **⚑ Smart Summary** Reservation of Inventory in SAP MM locks stock in advance for a cost center, production order, or stock transfer using MB21, then processes issues with MB1A, reversals with MBST, and closure with MB22. * πŸ”˜ **Purpose:** Reservations block quantities in MRP/ATP so a later document cannot consume the same stock unexpectedly. * β˜‘οΈ **MB21:** Create the reservation manually β€” pick movement type 201 for cost center, 261 for production order, or 311 for stock transfer. * βœ… **MB1A:** Post the goods issue referencing the reservation number, adjust quantity or storage location, then save to get the material document. * πŸ§ͺ **MBST:** Reverse the posted material document β€” SAP applies the reversal movement type (202 for a 201 issue) defined in OMJJ. * πŸ› οΈ **MB22:** Close a reservation for good by ticking the completed flag so it no longer participates in availability checks. * πŸ€– **AI Assist:** Copilot and AI-driven MM tools automate reservation creation from demand signals and flag stale reservations before they distort MRP. [ Read More ](javascript:void%280%29;) ![Reservation of Inventory in SAP MM](https://www.guru99.com/images/reservation-of-inventory-in-sap-mm.png) ## Reservation of Inventory in SAP Reservations are system documents that signal a requirement for a certain quantity of a material for production, a cost center, or any other need. Reservations matter in planning, MRP, and ATP because SAP earmarks the required quantities before they are posted. Without reservations, a production order might need materials that a sales order picked up minutes earlier. When you create a reservation, SAP blocks any other document from consuming that quantity for a different purpose. This behavior depends on the system settings for MRP and ATP. You can give reservations priority to always draw stock even when reserved by a sales order or delivery (not a clean solution), or configure sales orders to skip the reservation during availability checks. You can create a reservation for a material for many reasons. The system can also create the reservation automatically if the [MRP](https://www.guru99.com/material-requirement-planning-sap-pp.html) settings imply that behavior. This is done either automatically by the system or manually using the **MB21** transaction code. ## Reservation of Inventory by using MB21 **Step 1)** 1\. Execute transaction **MB21**. 2\. Fill in the fields as needed. [![Reservation of Inventory in SAP MB21 initial screen](https://www.guru99.com/images/sap/2013/05/052113_0555_33Reservati1.png)](https://www.guru99.com/images/sap/2013/05/052113%5F0555%5F33Reservati1.png) A reservation can be posted for consumption at a cost center (movement type 201), a production order (movement type 261), a stock transfer (311), a sales order, a project, a network, and so on. Choose the appropriate movement type. For this tutorial choose movement type **201**. If you enter movement type **321**, SAP throws an error message because that movement type cannot create a reservation. **Step 2)** 1\. Enter the cost center. 2\. Fill in the item data β€” material number, quantity, and source storage location. [![Reservation of Inventory in SAP MB21 item data](https://www.guru99.com/images/sap/2013/05/052113_0555_33Reservati2.png)](https://www.guru99.com/images/sap/2013/05/052113%5F0555%5F33Reservati2.png) Save the document. SAP returns a reservation number that you use in the next step. [![Reservation number confirmation in SAP MB21](https://www.guru99.com/images/sap/2013/05/052113_0555_33Reservati3.png)](https://www.guru99.com/images/sap/2013/05/052113%5F0555%5F33Reservati3.png) Now create a material document for the reservation. You can do that through MIGO, but this section covers another transaction. ## Reservation of Inventory by using MB1A Use transaction code **MB1A** to post a goods issue with reference to the material reservation. **Step 1)** 1\. Execute the transaction. 2\. Choose the **To Reservation…** button. [![Reservation of Inventory by using MB1A β€” To Reservation button](https://www.guru99.com/images/sap/2013/05/052113_0555_33Reservati4.png)](https://www.guru99.com/images/sap/2013/05/052113%5F0555%5F33Reservati4.png) **Step 2)** 1\. Enter the reservation number. 2\. Confirm. [![Reservation of Inventory by using MB1A β€” enter reservation number](https://www.guru99.com/images/sap/2013/05/052113_0555_33Reservati5.png)](https://www.guru99.com/images/sap/2013/05/052113%5F0555%5F33Reservati5.png) **Step 3)** 1\. Adjust any field β€” quantity, storage location, and so on β€” and save the document. [![Reservation of Inventory by using MB1A β€” save document](https://www.guru99.com/images/sap/2013/05/052113_0555_33Reservati6.png)](https://www.guru99.com/images/sap/2013/05/052113%5F0555%5F33Reservati6.png) SAP returns the material document number in the status bar message. [![Reservation of Inventory by using MB1A β€” material document number](https://www.guru99.com/images/sap/2013/05/052113_0555_33Reservati7.png)](https://www.guru99.com/images/sap/2013/05/052113%5F0555%5F33Reservati7.png) If the reservation needs to be reversed, use MIGO or the transaction covered next. ### RELATED ARTICLES * [ME47: How to Create Quotation in SAP MM ](https://www.guru99.com/how-to-create-quotations.html "ME47: How to Create Quotation in SAP MM") * [How to Post Goods Receipt: SAP MIGO ](https://www.guru99.com/how-to-post-goods-receipt.html "How to Post Goods Receipt: SAP MIGO") * [How to Create Goods Receipt in SAP: MIGO, MB1C, MB03 ](https://www.guru99.com/how-to-create-goods-receipt.html "How to Create Goods Receipt in SAP: MIGO, MB1C, MB03") * [Outline Agreement in SAP: Contract & Scheduling Agreement ME31 ](https://www.guru99.com/all-about-outline-agreement.html "Outline Agreement in SAP: Contract & Scheduling Agreement ME31") ## Reservation of Inventory by using MBST **Step 1)** 1\. Execute the **MBST** transaction code. 2\. Enter the document number created in the previous step and press **ENTER**. [![Reservation of Inventory by using MBST β€” enter document number](https://www.guru99.com/images/sap/2013/05/052113_0555_33Reservati8.png)](https://www.guru99.com/images/sap/2013/05/052113%5F0555%5F33Reservati8.png) **Step 2)** SAP uses movement type **202** for this purpose β€” the reversal for a cost-center issue. That mapping is set up in **OMJJ**, which defines 202 as the reversal movement type for 201. Save the transaction data and the previous document is reversed. [![Reservation of Inventory by using MBST β€” reversal saved](https://www.guru99.com/images/sap/2013/05/052113_0555_33Reservati9.png)](https://www.guru99.com/images/sap/2013/05/052113%5F0555%5F33Reservati9.png) Now you can create a material document for the same reservation again, or **close the reservation** itself using t-code **MB22**. ## Reservation of Inventory by using MB22 **Step 1)** 1\. Execute the transaction. 2\. Enter the reservation number and press **ENTER**. [![Reservation of Inventory by using MB22 β€” enter reservation number](https://www.guru99.com/images/sap/2013/05/052113_0555_33Reservati10.png)](https://www.guru99.com/images/sap/2013/05/052113%5F0555%5F33Reservati10.png) **Step 2)** Tick the check box to mark the reservation completed (SAP will not expect further goods postings on this reservation). [![Reservation of Inventory by using MB22 β€” mark completed](https://www.guru99.com/images/sap/2013/05/052113_0555_33Reservati11.png)](https://www.guru99.com/images/sap/2013/05/052113%5F0555%5F33Reservati11.png) The reservation is now dismissed from further processing. ## FAQs ⚑ What is a reservation of inventory in SAP MM? A reservation is an SAP MM document that earmarks a specified material quantity for a future goods movement β€” such as a production order, cost center, or stock transfer β€” so MRP and availability checks respect that commitment. 🧾 Which movement types are used with reservations? Common types are 201 (cost center), 261 (production order), 311 (stock transfer within plant), plus 202 and 262 as their reversals. Choose the type that matches the receiving object; SAP blocks incompatible types like 321 at MB21. πŸ—‚οΈ Which tables store SAP reservation data? SAP stores reservation headers in table RKPF and reservation items in table RESB. Reports like MB25 read these tables to list open reservations by material, plant, cost center, or production order. πŸ” How does MBST differ from MB22? MBST reverses a posted material document (undoes the goods movement) using the reversal movement type from OMJJ. MB22 changes the reservation itself β€” typically ticking the completed flag so no further postings are expected. πŸ“ˆ Do reservations affect MRP and ATP? Yes. Reservations create dependent demand that MRP includes when calculating requirements, and ATP subtracts open reservation quantities from available stock. Customizing controls whether sales orders check reservations during availability checks. πŸ” Which SAP report lists open reservations? Transaction MB25 (program RM07RESL) lists reservations by plant, material, cost center, or account assignment. It shows open, completed, and released status so planners can clean up stale reservations before month-end. πŸ€– How can AI help manage reservations? AI-driven MM analytics detect reservations that never converted to a goods issue, flag duplicate reservations for the same demand, and recommend closure so MRP stops locking phantom stock. Machine-learning models forecast reservation demand from historical patterns. 🧠 Can Copilot automate MB21 reservation creation? Copilot for SAP can draft BAPI\_RESERVATION\_CREATE1 calls or GUI-scripting steps for MB21 from a plain-English demand list, mapping material, quantity, cost center, and movement type. Consultants review the script before it runs against production. #### Summarize this post with: ChatGPT Perplexity Grok Google AI **Stay Updated on AI** **Get Weekly AI Skills, Trends, Actionable Advice.** ##### Sign up for the newsletter Subscribe for Free You have successfully subscribed. Please check your inbox. ![AI-Newsletter](https://www.guru99.com/images/footer-email-avatar-imges-1.png) Chosen by over **350,000+** professionals [Scroll to top ](#wrapper)Scroll to top Γ— Toggle Menu Close Search for: Search ```json {"@context":"https://schema.org","@graph":[{"@type":"Organization","@id":"https://www.guru99.com/#organization","name":"Guru99","sameAs":["https://www.facebook.com/Guru99Official","https://twitter.com/guru99com"],"logo":{"@type":"ImageObject","@id":"https://www.guru99.com/#logo","url":"https://www.guru99.com/images/guru99-logo-v1-150x59.png","contentUrl":"https://www.guru99.com/images/guru99-logo-v1-150x59.png","caption":"Guru99","inLanguage":"en-US"}},{"@type":"WebSite","@id":"https://www.guru99.com/#website","url":"https://www.guru99.com","name":"Guru99","publisher":{"@id":"https://www.guru99.com/#organization"},"inLanguage":"en-US"},{"@type":"ImageObject","@id":"https://www.guru99.com/images/reservation-of-inventory-in-sap-mm.png","url":"https://www.guru99.com/images/reservation-of-inventory-in-sap-mm.png","width":"700","height":"250","caption":"Reservation of Inventory in SAP MM","inLanguage":"en-US"},{"@type":"BreadcrumbList","@id":"https://www.guru99.com/reservation-of-inventory.html#breadcrumb","itemListElement":[{"@type":"ListItem","position":"1","item":{"@id":"https://www.guru99.com","name":"Home"}},{"@type":"ListItem","position":"2","item":{"@id":"https://www.guru99.com/sap-mm","name":"SAP - MM"}},{"@type":"ListItem","position":"3","item":{"@id":"https://www.guru99.com/reservation-of-inventory.html","name":"Reservation of Inventory in SAP MB21, MB1A, MBST, MB22"}}]},{"@type":"WebPage","@id":"https://www.guru99.com/reservation-of-inventory.html#webpage","url":"https://www.guru99.com/reservation-of-inventory.html","name":"Reservation of Inventory in SAP MB21, MB1A, MBST, MB22","dateModified":"2026-07-07T11:58:40+05:30","isPartOf":{"@id":"https://www.guru99.com/#website"},"primaryImageOfPage":{"@id":"https://www.guru99.com/images/reservation-of-inventory-in-sap-mm.png"},"inLanguage":"en-US","breadcrumb":{"@id":"https://www.guru99.com/reservation-of-inventory.html#breadcrumb"}},{"@type":"Person","@id":"https://www.guru99.com/author/olivia","name":"Olivia Turner","description":"I'm Olivia Turner, an SAP MM, QM, PP, and PI/PO Consultant, specializing in optimizing SAP systems for manufacturing and quality management.","url":"https://www.guru99.com/author/olivia","image":{"@type":"ImageObject","@id":"https://www.guru99.com/images/olivia-turner-author-120x120.png","url":"https://www.guru99.com/images/olivia-turner-author-120x120.png","caption":"Olivia Turner","inLanguage":"en-US"},"worksFor":{"@id":"https://www.guru99.com/#organization"}},{"articleSection":"SAP - MM","headline":"Reservation of Inventory in SAP MB21, MB1A, MBST, MB22","description":"Reservations are system documents that show a requirement for a certain amount of good for production, cost center and any other need. 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