This document explains how the Planning Worksheet action Calculate Purchase Plan decides whether to create a planning worksheet line and how it calculates the quantity to to purchase. It is written for Business Central users and consultants who want to understand the planning result.

Differences between base Business Central and the Calculate Purchase Plan from the Enhanced Planning Worksheet

The Purchase Plan is not time phased and inventory cannot go below zero and/or safety stock with safety stock being the new zero point if set; furthermore, demand is automatically consolidated into a single requisition line. The Regenerative Plan is the same logic as the Business Central Planning Worksheet and is time phased.

A detailed walkthrough explaining this is available here: https://youtu.be/yCgA2blAPRk?si=g-ZPiBOs6OCZ4_hJ

Calculate Purchase Plan reviews the Stockkeeping Units (SKUs) that match the filters entered on the request page. For each planned SKU, it:

1. Determines whether the SKU should be included in the run.
2. Calculates demand for the SKU, location, and variant.
3. Calculates the quantity available after considering existing supply and demand.
4. Applies the SKU’s reordering policy.
5. Applies rounding, minimum order quantity, and order multiple rules.
6. Creates a planning worksheet line when the final suggested quantity is greater than zero.

The same quantity calculation is used for purchase and transfer suggestions. The SKU’s Replenishment System determines whether the resulting planning worksheet line is for a purchase, transfer, production order, or assembly replenishment.

The most important options are:

This option is especially important for SKUs with Reordering Policy = Maximum Qty.:

• Use Reorder Point: reorder is triggered when net available quantity is at or below Safety Stock Quantity + Reorder Point.
• Use Maximum Qty.: reorder can be triggered to top the SKU up toward Maximum Inventory even when net available quantity is still above the reorder point.

The run starts with the SKU filters entered on the request page, such as item, location, and vendor filters. SKUs without a reordering policy are not planned.

The Plan replenishment for option further limits the included SKUs:

Blocked items are skipped. Blocked vendors are also skipped when creating worksheet lines.

For each SKU, actual demand is calculated as:

Actual Demand = Transfer Order Shipment Quantity
              + Sales Demand
              + Service Demand

This is the outstanding transfer shipment demand for the SKU’s item, location, and variant. It represents quantity expected to leave the location through transfer orders.

Sales demand

Sales demand is based on outstanding sales quantities for the item, location, and variant:

Sales Demand = Outstanding Sales Orders and Invoices

Depending on Enhanced Planning Worksheet Setup, sales demand may include all applicable sales documents or only released sales documents.

Sales return orders are not subtracted from Sales Demand. Instead, qualifying sales return quantities are treated as incoming supply when Net Available is calculated. The Include Sales Returns setting on the Enhanced Planning Worksheet Setup page determines which sales return orders are included.

Service demand is based on outstanding service quantities for the item, location, and variant:

Service Demand = Outstanding Service Orders and Invoices
               - Outstanding Service Credit Memos

Enhanced Planning setup determines whether service demand is ignored, limited to open service documents, or limited to released-to-ship service documents.

If a forecast name is supplied, forecast demand is calculated for the item, location, and variant over this period:

Work Date through Forecast End Date

The plan sums forecast quantities in that period. If the forecast quantity is positive, actual sales usage in the same period is deducted from the forecast.

Forecast Demand = Forecast Quantity in the Forecast Period
                - Actual Sales Usage in the Forecast Period

If no forecast name is supplied, forecast demand is zero.

If the user’s Consumption Qty Behavior preference is set to include consumption quantities, component demand is also subtracted:

Net Available = Net Available
              - Quantity on Component Lines
              - Quantity on Assembly Components

If Include Planned Purchases is set to include planned purchases, existing planning worksheet receipt quantities are added as supply:

Net Available = Net Available
              + Purchase Requisition Receipt Quantity

If planned purchases are not included, existing planning worksheet receipt quantities are ignored. This may produce a larger new suggestion, especially when old planning worksheet lines are retained.

After net available quantity is calculated, the SKU’s reordering policy determines the suggested quantity.

For Lot-for-Lot and Order, the plan replenishes up to safety stock:

Suggested Quantity = max(Safety Stock Quantity - Net Available, 0)

If net available quantity is already greater than or equal to safety stock, no line is suggested.

For Maximum Qty., the plan first determines whether reorder should be triggered.

With Minimum Level to Trigger Reorder = Use Reorder Point, the trigger is:

Safety Stock Quantity + Reorder Point >= Net Available

With Minimum Level to Trigger Reorder = Use Maximum Qty., the plan can reorder up to maximum even when the SKU has not fallen to the reorder-point trigger level.

When a reorder is triggered, the suggested quantity is the larger of these two values:

Maximum Inventory - Net Available
Safety Stock Quantity + Reorder Point - Net Available

So, in practical terms, the plan usually tops the SKU up toward Maximum Inventory, while also ensuring the suggestion covers any shortage below the safety-stock-plus-reorder-point level.

For Fixed Reorder Qty., reorder is triggered when:

Safety Stock Quantity + Reorder Point >= Net Available

When triggered, the plan starts with the larger of:

Reorder Quantity
Safety Stock Quantity + Reorder Point - Net Available

That quantity is rounded up using the reorder quantity as the rounding increment.

After the reordering policy calculates the base suggested quantity, the plan applies these final adjustments:

1. Rounding precision: the quantity is rounded using the item’s rounding precision. If no rounding precision is defined, the plan rounds to 0.01.
2. Minimum order quantity: if the suggested quantity is greater than zero, it is increased to at least the SKU’s minimum order quantity.
3. Order multiple: if an order multiple is defined, the quantity is rounded up to the next order multiple.
4. Zero or negative result: if the final result is not greater than zero, no worksheet line is created.

When the final quantity is greater than zero, a planning worksheet line is created.

The line uses:

• The SKU’s item, variant, and location.
• Action Message = New.
• The calculated quantity, converted from base units to the worksheet line unit of measure if necessary.
• Order Date = Work Date.
• Due Date = Work Date + Lead Time Calculation from the SKU.
• Accept Action Message = Yes.
• For transfer replenishment, the transfer shipment date is set from the due date.

The selected batch option determines where the line is created. If a specific batch is selected, that batch is used. Otherwise, the user’s planning worksheet batch preferences are used.

The calculation of the quantity is the same for purchase and transfer replenishment. The difference is the SKU’s replenishment system:

• A purchase SKU creates a purchase planning suggestion.
• A transfer SKU creates a transfer planning suggestion.

For transfer SKUs, transfer-specific fields such as transfer shipment date are populated, but the suggested quantity comes from the same net-availability and reordering-policy formulas described above.

Calculate Purchase Plan does not recursively use transfer suggestions created during the current run as demand at the transfer-from location. For example, forecast demand at one location may create a transfer suggestion from a second location, but that planning worksheet line does not immediately become transfer shipment demand for the supplying SKU. Transfer shipment demand includes existing transfer orders, not newly proposed worksheet lines. To generate the related purchase suggestion, first carry out the transfer suggestion to create the transfer order, and then run Calculate Purchase Plan again. For planning scenarios that must propagate demand through multiple replenishment levels in a single calculation, use Calculate Regenerative Plan instead.

Assume a purchase SKU has these values:

First, choose demand:

Demand To Use = max(25, 15) = 25

Then calculate net available:

Net Available = 20 + 0 + 10 + 0 + 0 - 25 = 5

For Maximum Qty., the trigger level is:

Safety Stock Quantity + Reorder Point = 5 + 10 = 15

Because net available quantity is 5, the reorder is triggered.

The suggested quantity is:

Maximum Inventory - Net Available = 60 - 5 = 55
Safety Stock Quantity + Reorder Point - Net Available = 15 - 5 = 10
Suggested Quantity = max(55, 10) = 55

Before the worksheet line is created, this quantity is still subject to item rounding precision, minimum order quantity, and order multiple rules.

Assume a transfer SKU has the same quantities as Example 1. The demand, net available quantity, trigger, and suggested quantity are identical:

Suggested Quantity = 55

Because the SKU is a transfer SKU, the worksheet line is a transfer suggestion instead of a purchase suggestion. The quantity is still 55 before rounding, minimum order quantity, and order multiple adjustments.

Assume the same purchase SKU as Example 1, but there is already an existing planning worksheet receipt quantity of 20.

If Include Planned Purchases is not selected:

Net Available = 20 + 0 + 10 + 0 + 0 - 25 = 5
Suggested Quantity = 55

If Include Planned Purchases is selected:

Net Available = 20 + 0 + 10 + 0 + 0 - 25 + 20 = 25

With Minimum Level to Trigger Reorder = Use Reorder Point, the Maximum Qty. reorder trigger is not met because:

Safety Stock Quantity + Reorder Point = 15
Net Available = 25

In that case, no new line is suggested. This is why the Include Planned Purchases option can significantly change the result when existing planning worksheet lines are present.