Item tracking in AL: lots, serials and the Reservation Entry table

The first time an extension creates a sales line for a lot-tracked item and tries to post it, it fails: "You must assign a lot number". The lot is not on the line. It is in a separate structure that most developers meet only when something breaks. This is that structure.

Where tracking lives

Table 337 Reservation Entry holds, for each document line that needs it, one entry per lot/serial/package and quantity, with "Source Type", "Source Subtype", "Source ID", "Source Ref. No." pointing back at the line (table, document type, document no., line no.) and "Reservation Status" (Reservation, Tracking, Surplus, Prospect). The same table holds reservations against supply; tracking is the Surplus and Tracking status entries with lot or serial filled in. On posting, the item journal line is split by these entries and each becomes an Item Ledger Entry with the lot/serial, which is where the stock-by-lot comes from (Item Ledger Entry with "Lot No.", summarised through "Lot No. Information" and the availability pages).

The Item Tracking Code on the item says what is tracked (lot, serial, package) and when it is required (inbound, outbound, warehouse); the Tracking Specification table (336) is the temporary working shape used by the item tracking lines page and the codeunits.

Assigning tracking from code

Do not insert Reservation Entries by hand. Use the codeunits the base application uses:

var
    CreateReservEntry: Codeunit "Create Reserv. Entry";
    ReservEntry: Record "Reservation Entry";
begin
    CreateReservEntry.CreateReservEntryFor(
        Database::"Sales Line", SalesLine."Document Type".AsInteger(), SalesLine."Document No.", '', 0, SalesLine."Line No.",
        SalesLine."Qty. per Unit of Measure", Qty, QtyBase, ReservEntry);
    CreateReservEntry.SetNewTrackingFromNewTrackingSpecification(TempTrackingSpecification); // lot/serial set on the spec
    CreateReservEntry.CreateEntry(SalesLine."No.", SalesLine."Variant Code", SalesLine."Location Code", SalesLine.Description,
        SalesLine."Shipment Date", 0D, 0, ReservEntry."Reservation Status"::Surplus);
end;

For the common "assign this lot to this line" case, Codeunit "Item Tracking Management" and the "Item Tracking Lines" page's RegisterItemTrackingLines procedure, driven from a temporary Tracking Specification, is the supported path and handles quantity checks, serial uniqueness and availability. For receipts, "Item Tracking Doc. Management" helps copy tracking from one document to another (receipt to put-away, order to shipment).

Reading it

To find the lots on a line: ReservEntry.SetSourceFilter(Database::"Sales Line", DocType, DocNo, LineNo, true) (the helper on the record) and read "Lot No.", "Serial No.", "Quantity (Base)". To find stock by lot: Item Ledger Entry filtered on item, location and lot with "Remaining Quantity", or the "Lot No. Information" FlowFields.

What goes wrong

• Creating lines from an integration without tracking, for items whose tracking code requires it outbound. Either assign tracking in the integration or leave it to the warehouse pick, where tracking can be assigned on the pick for items set up that way.
• Expiration dates: if the tracking code requires them, they are on the entry ("Expiration Date") and must be set on inbound; outbound takes them from the lot.
• Deleting a line without deleting its reservation entries (use the line's Delete(true), which calls the reservation management clean-up).
• Quantity on tracking not equal to quantity on the line: the posting check fails. Keep them in step; the tracking page does, your code must.

For regulated industries (food, pharma) this table is the audit trail; the partner due diligence post has more on why the partner must know it.

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