Mastering Custom B2B Payment Terms: EOM + Days Calculations on Shopify

Hey fellow store owners! Let's talk about something many of us in the wholesale game wrestle with: those custom payment terms like "X days after End of Month" (EOM) or "End of the following month." It's a common request, and if you're like @HaldexD2D in the Shopify community, you're probably tired of manually calculating due dates or paying for expensive apps to handle it.

The good news? The Shopify community has been buzzing with some really clever, code-based solutions using Shopify's built-in tools like Flow and Functions. While Shopify doesn't have these exact EOM calculations natively baked into its B2B payment terms just yet (a popular feature request, for sure!), there are robust ways to automate this crucial part of your wholesale operations.

The Core Challenge: Getting EOM Dates Right

As @Lauren_Scott and @paulvatiche highlighted in the discussion, the devil is in the details, especially when it comes to date math. Things like leap years, varying month lengths, and the critical distinction between an order date and an invoice date can throw a wrench into your calculations. For example, an order placed on October 31st but invoiced on November 1st will have a different due date depending on which date you use as your starting point. Most EOM terms are based on the invoice month, so keeping that straight is key.

Two Main Paths to Automation

The community discussion pointed towards two primary, powerful methods for automating these complex payment terms:

1. Automating Due Dates for Orders with Shopify Flow

This is probably the most flexible solution, especially if your team creates a mix of orders and draft orders. @Daniel_Jude laid out a fantastic approach using Shopify Flow, which is free to use and incredibly powerful. Here's how it generally works:

Step-by-Step: Setting EOM Payment Terms with Shopify Flow

1. Trigger the Workflow: Start your Flow whenever an order is created. This ensures the due date is calculated right away.
2. Calculate the Due Date with a 'Run Code' Step: This is where the magic happens. You'll use a JavaScript snippet to perform the EOM calculations. As @Lauren_Scott stressed, make sure to base your calculations on the invoice month. You'll pass the order's creation date (or your determined invoice date) into the 'Run Code' step as an input.

Here's a simplified look at the JavaScript logic for calculating the last day of a month and adding days:

// Assuming 'invoiceDate' is passed in as a JavaScript Date object
let y = invoiceDate.getFullYear();
let m = invoiceDate.getMonth(); // JavaScript months are 0-indexed (Jan is 0, Dec is 11)

// To get the last day of the invoice month:
let lastDayOfInvoiceM Date(y, m + 1, 0);

// To get the last day of the *following* month:
let lastDayOfFollowingM Date(y, m + 2, 0);

// For 'X days after EOM', add X days to lastDayOfInvoiceMonth.
// Example for 30 days after EOM:
lastDayOfInvoiceMonth.setDate(lastDayOfInvoiceMonth.getDate() + 30);

// Format the result as 'YYYY-MM-DD' to avoid timezone issues
let dueDate = lastDayOfInvoiceMonth.toISOString().slice(0, 10);
// Or for EOM following month:
// let dueDate = lastDayOfFollowingMonth.toISOString().slice(0, 10);

Remember, the JavaScript Date object is smart enough to handle month lengths and even leap years, so you don't have to code those complexities yourself! Just make sure to return the result as a plain YYYY-MM-DD string to avoid any timezone mishaps, as @Lauren_Scott wisely cautioned.

3. Set the Due Date with 'Send Admin API Request': Once your 'Run Code' step calculates the correct due date, you'll use a 'Send Admin API Request' action in Flow. This step leverages the paymentTermsUpdate mutation to directly set the due date on the order's payment schedule. This is crucial because, as @Lauren_Scott pointed out, you want to update the actual payment schedule, not just a metafield that changes wording.

What About Draft Orders?

Here's a small catch: the paymentTermsUpdate mutation currently only applies to regular orders, not draft orders. For draft orders, @gavin_turner suggested using Flow to set a metafield with the calculated date. While this works as a visual workaround and helps your team, it's important to remember it won't officially update the payment schedule in the same way. You'd still need to manually set the official due date once the draft order is converted or use a separate process.

2. Payment Customization Function for B2B Checkouts

For those of you with wholesale buyers who check out themselves through company accounts, @Arslan_Shopify_Dev brought up an interesting, newer route: a payment customization Function. This method is specifically designed to run during the B2B checkout process.

The Function receives the shop's local date as an input, allowing you to compute the last day of the month plus your specified X days. You then set a fixed due date, and the order is created with this correct date. This is a powerful, built-in way to customize the checkout experience without relying on external apps.

However, keep these points in mind:

• It only runs during the checkout process. Draft orders created by your team in the admin will still need a Flow-based approach.
• It uses the checkout date, which again highlights the `invoice-date vs order-date` debate. You'll need to decide if the checkout date aligns with your definition of the invoice date for your EOM terms.
• Always double-check the plan and API requirements in the current Shopify documentation before diving into building a Function.

Critical Considerations and Testing

Regardless of which path you choose, a few things are absolutely critical:

• Invoice Date vs. Order Date: This came up multiple times in the discussion. Ensure your logic consistently uses the date you define as the 'invoice date' for calculating EOM terms.
• Testing, Testing, Testing: As @Lauren_Scott wisely advised, test thoroughly! Run through scenarios like a November invoice, a January invoice (to check leap year handling), and especially orders placed at month boundaries (e.g., Oct 31st invoiced Nov 1st) to ensure your rules behave exactly as intended.
• Leverage Shopify's Extensibility: These solutions truly showcase the power of Shopify's platform. If you're building out a new wholesale operation or looking to optimize an existing one, exploring these built-in tools can save you a ton of time and money. If you're just starting your B2B journey or looking to expand, remember that Shopify offers a robust platform that can be tailored to complex business needs like these.

While we all hope Shopify eventually offers these specific EOM payment term calculations as a native, out-of-the-box feature, the community has clearly shown that you don't have to wait. By combining Shopify Flow's automation capabilities with a little JavaScript, or by leveraging payment customization Functions for B2B checkouts, you can build a robust, cost-effective solution that handles your complex payment terms with precision. It might take a bit of initial setup, but the automation and accuracy will be well worth it!