ERP AP Automation: Invoices, Retainage, and Prepayments

By | February 25, 2026
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In today’s fast-moving business landscape, Accounts Payable (AP) teams and ERP users are expected to do more with less — faster processing, fewer errors, and better financial visibility. Yet many organizations still rely on manual data entry, multiple tools, and disconnected workflows that slow down invoice processing and prepayment tracking.

That’s why Sage 300 AP Integration, a modern API designed to simplify AP Invoice and Prepayment management seamlessly within your ERP environment. Whether you handle standard vendor bills, retainage holds, advance payments, or linked transactions — AP Integration makes these processes automated, transparent, and auditable.

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The Need for API:

AP processes frequently become bottlenecks when teams struggle with:

  • Manual entry of invoices and prepayment records
  • Difficulty handling retainage and payments consistently
  • Time lost in reconciling vendor accounts and approvals

For ERP end users, these challenges mean delays, inefficiencies especially in industries like construction, professional services, manufacturing, and projects with complex billing structures.

AP Integration was designed to solve these exact challenges by automating invoice creation from normal invoices to retainage and prepayment — with minimal effort and maximum accuracy.

What AP Integration Does

The API handles every stage of invoice and prepayment management.
Here’s how it works:

1. Normal Invoice Creation

Figure 1 AP Invoice Json

Figure 2 AP Invoice Batch

A normal invoice represents a standard bill from a vendor for goods delivered or services rendered.

API Functionality:

  • Accept invoice details such as vendor ID, invoice date, due date, line items, taxes.
  • Validate entries against business rules (e.g., GL codes, vendor status).
  • Create the invoice in the ERP and assign a unique invoice ID.

Benefits:

  • Eliminates manual invoice entry
  • Reduces human error
  • Standardizes data across system.

2. Retainage Invoice Creation

Figure 3 AP Retainage Invoice JSON

Figure 4 AP Retainage Invoice Batch


Retainage is a common requirement where a percentage of payment is held back until work is complete or quality is assured.

API Functionality:

  • Generate a retainage invoice linked to the original invoice (using a service ID or reference).
  • Automatically calculate the retainage amount based on predefined business rules.
  • Record the retainage separately with a link to the original invoice.

Benefits:

  • Clear tracking of retained amounts
  • Simplifies contract compliance and accounting
  • Eliminates manual recalculations

3. Prepayment Creation

Figure 5 AP Prepayment JSON

Figure 6 AP Prepayment Batch

A prepayment represents an advance payment made before goods are delivered or services begin.

API Functionality:

  • Create prepayment with vendor references, amounts, currency.
  • Link prepayment entries to future invoices.
  • Adjust vendor advance balances automatically in the ERP.

Benefits:

  • Tracks advance payments with precision
  • Ensures later settlements are accurate
  • Improves cash flow visibility

About Us:-

Greytrix – a globally recognized and one of the oldest Sage Gold Development Partner is a one-stop solution provider for Sage ERP and Sage CRM organizational needs. Being acknowledged and rewarded for multi-man years of experience, we bring complete end-to-end assistance for your technical consultations, product customizations, data migration, system integrations, third party add-on development and implementation competence.

Greytrix offers unique GUMU™ integrated solutions of  Sage 300 with Sage CRM, Salesforce.com, Dynamics 365 CRM and MagentoeCommerce along with Sage 300 Migration from Sage 50 US, Sage 50 CA, Sage PRO, QuickBooks, Sage Business Vision and Sage Business Works. We also offer best-in-class Sage 300 customization and development services and integration services for applications such as POS | WMS | Payroll | Shipping System | Business Intelligence | eCommerce for Sage 300 ERP and for Sage 300c development services we offer, upgrades of older codes and screens to new web screens, latest integrations using Data and web services to Sage business partners, end users and Sage PSG worldwide.Greytrix offers 20+ addons for Sage 300 to enhance productivity such as GreyMatrix, Document Attachment, Document Numbering, Auto-Bank Reconciliation, Purchase Approval System, Three way PO matching, Bill of Lading and VAT for Middle East. The GUMU™ integration for Dynamics 365 CRM – Sage ERP is listed on Microsoft Appsource with easy implementation package.

For more details on Sage 300 and Sage 300c Services, please contact us at accpac@greytrix.com, We will like to hear from you.

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