SAP standard does not do an availability check on the quotation, as it is not a definite order, usually just a pricing quote.

When it is converted to an order, the first availability check is carried out, as well as credit checks.  The system will check stock in the plant, plus what is contained in the availability checking rule (scope of check) eg: can add POs for replenishment, purchase reqs, different planned orders, and subtract sales orders, deliveries etc already created against that material in that plant (and possibly Storage location).

If there is enough stock in the plant/SLoc, the system will give you a confirmed date, or give you a date based on the production time or purchasing time from the material master.  The date the system proposes is based on the customer's requested delivery date.

SAP first backward schedules looking at the required delivery date, less transportation time, less transportation lead time, less pick and pack time, less production/purchase time if applicable.  If the date it calculates is equal or later than today’s date, then it will confirm the customer’s required date.  If it falls in the past, SAP will then forward schedule for today’s date, plus the times listed above to get the date when the customer can actually have it.

ATP is the single most complex part of the SD module, depending upon how PP and MRP is set up.

MRP works semi-separately, depending on how it is set up.  Basically, MRP looks at the demand on the plant, and if it the stock does not meet expected sales orders and deliveries, it will create a purchase requisition (outside purchase) or requirement or planned order (for production) to cover the shortfall.  When MRP is started, it will turn the PR into a PO or the requirement into a production order.

Other SD Queries:

• SAP SD CIN Configuration
• SD Questions About Pricing Condition

SAP Sales and Distribution Books
SAP SD Books - Certification, Interview Questions and Configuration

SAP Sales and Distribution Tips
SAP SD Discussion Forum and Sales/Distribution Tips

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