Typically, grain fees are calculated on a monthly basis. If the end of grace days is on or before the date grain fees are calculated, then storage fees are charged from Day 1. 

If Grace Days = 10, the producer has 10 days to transfer a receipt to Open Storage or Link to Contract.
If the producer waits until Day 11, storage fees will be calculated as of Day 1.  

If Grace Days = 10 and Omit grace days charge is checked,
if the producer waits until Day 11 storage fees will be calculated as of Day 11

Individual customers may have grace periods and rates that override commodity defaults.

When moved out of producer storage, remaining unbilled storage fees will be added to the receipt which will follow through to the settlement.

Grading Factor adjustments included in monthly fees are also calculated and added (e.g. Drying Fees).

Grain fees are calculated per receipt line and are combined into a suggested invoice amount (detailed information about the individual chargeable items is also available).

Once you apply grain fees, invoices are created with applicable fees, and producer accounts are updated.

Grain Fee invoices have interest rates and chargeable dates. Interest rates are determined the same way AR invoice interest rates are.

I want to read the white paper (with lots of screenshots) about calculating Monthly Grain Fees.

What You'll Find:

Calculating Grain Fees

Use the Monthly Grain Fees window to calculate grain fees. Any fees already calculated are not affected.

You can calculate grain fees for some or all producers from one location or all locations.

To calculate grain fees

Navigate to Grain > Monthly Grain Fees.
The Monthly Grain Fees window opens.

Select the Start Date, End Date, Location, and Commodity.

Highlight the Grain Fees to calculate.
(all fees are selected by default, click to deselect)

Calculate for All Customers, or select This Customer to calculate for a single producer.

Select the Invoice Date.
(defaults to Today, can be changed)

The Due Date and Chargeable Date are determined by default Interest Settings.
(can be changed)

Created By defaults to the logged in user.
(can be changed)

Add any Comments to accompany the storage fees.

Click Retrieve.
All receipts in producer storage that meet the criteria are listed along with their total amounts.

(optional) Uncheck Charge next to any producers you don't want to charge.
Any producers being waived for this cycle can be excluded by clearing the Charge check box.

(optional) Select a receipt row and click Edit to view more details.
The Monthly Grain Fees - Receipts window opens.

(optional) Select Edit to change a Rate, or to not charge a particular fee.
The Monthly Grain Fees - Adjustments window opens.
(e.g. you could edit the storage fee adjustment rate to zero to show that storage fees are still charged but have $0 value for this cycle)

Make your changes.

Select Update to save.
The Monthly Grain Fees - Adjustments window closes.

Select Update to save your receipt changes.
The Monthly Grain Fees - Receipts window closes.

Select Save to create the grain fee invoices.

Editing Grain Fees

Edit the grain invoice created to record the grain fees.