5. Purchase Module

The Purchase Module manages the complete procurement cycle in NkapBooks — from recording vendor bills to making payments and tracking supplier relationships. It is accessible from the Purchases section in the sidebar and contains the following sub-modules:

5.1 Purchase Invoices

Purchase Invoices (also called vendor bills or purchase bills) record amounts owed to suppliers for goods or services received. Each submitted purchase invoice generates double-entry accounting ledger entries and tracks the outstanding amount until fully paid.

Schema Overview

Purchase Invoice Item Fields

Each line item in a Purchase Invoice includes:

Settings Tab

The Purchase Invoice form includes a Settings tab with the following options:

Document Lifecycle

┌─────────┐      ┌───────────┐      ┌──────────┐
│  Draft   │─────▶│ Submitted │─────▶│   Paid   │
│          │      │           │      │          │
└─────────┘      └─────┬─────┘      └──────────┘
                       │
                       ▼
                 ┌───────────┐
                 │ Cancelled │
                 └───────────┘

Accounting Entries (on Submit)

When a Purchase Invoice is submitted, the following ledger entries are created:

Key Features

• Automatic Tax Calculation — Taxes are computed automatically based on the tax template assigned to each item.
• Multi-Currency Support — Purchase invoices can be issued in the supplier's currency. The exchange rate is fetched automatically and all amounts are stored in both the transaction currency and the company's base currency.
• Auto Payment — Enable "Make Payment On Submit" to automatically create and submit a payment entry when the invoice is submitted.
• Auto Purchase Receipt — Enable "Make Purchase Receipt On Submit" to automatically receive goods into inventory when the invoice is submitted.
• Invoice Returns (Debit Notes) — Create return invoices to record goods returned to suppliers. Returns reverse the original accounting entries and update the original invoice's outstanding amount.
• Discount Accounting — Apply discounts at both the item level and the invoice level, either before or after tax.
• Price Lists — Apply purchase-specific price lists to automatically set item rates.
• License Tracking — Invoice creation is tracked against your license tier limits (does not apply to return invoices).

Actions

The following actions are available from a Purchase Invoice:

List View

The Purchase Invoice list displays the following columns:

Workflow: Creating a Purchase Invoice

1. Navigate to Purchases → Purchase Invoices in the sidebar.
2. Click ＋ New to create a new Purchase Invoice.
3. Select the Supplier — the payables account and currency are auto-filled from the supplier record.
4. Add line items:
   • Select an Item — the rate, tax, and description are auto-filled from the item record.
   • Adjust the Quantity and Rate as needed.
   • Optionally apply per-item discounts.
5. Optionally apply an invoice-level discount.
6. Review the automatically calculated Net Total, Taxes, and Grand Total.
7. Optionally enable Make Payment On Submit and/or Make Purchase Receipt On Submit in the Settings tab.
8. Click Save to save as Draft, or Submit to finalize the invoice.

5.2 Purchase Payments

Purchase Payments record money paid to suppliers against purchase invoices. Payments are handled by the unified Payment document type with paymentType: "Pay".

Schema Overview

Payment Reference (PaymentFor) Fields

Each payment can reference one or more Purchase Invoices:

Document Lifecycle

┌─────────┐      ┌───────────┐
│  Draft   │─────▶│ Submitted │
│          │      │           │
└─────────┘      └─────┬─────┘
                       │
                       ▼
                 ┌───────────┐
                 │ Cancelled │
                 └───────────┘

Accounting Entries (on Submit)

When a Purchase Payment is submitted:

With Taxes (e.g., TDS/Withholding Tax):

Key Features

• Multi-Invoice Payments — A single payment can be applied against multiple purchase invoices simultaneously. Add multiple entries to the Payment Reference table.
• Partial Payments — Pay less than the full outstanding amount. The invoice's outstanding balance is updated automatically.
• Write-Off — Write off small remaining balances when the payment amount doesn't exactly match the outstanding amount. The difference is posted to the configured Write Off Account.
• Multiple Payment Methods — Support for Cash, Bank Transfer, Cheque, and custom payment methods. Each payment method can have a default account configured.
• Automatic Account Selection — When a Payment Method is selected, the From/To accounts are automatically set based on the payment method's configured accounts and the payment type.
• Tax on Payment — Supports withholding tax (TDS) or other taxes applied at payment time, with separate accounting entries.
• Reference Tracking — Record cheque numbers, bank reference IDs, and clearance dates for bank reconciliation.
• Outstanding Amount Validation — The system validates that the payment amount does not exceed the total outstanding amount across all referenced invoices.

Workflow: Making a Purchase Payment

1. From a Purchase Invoice: Open a submitted Purchase Invoice with outstanding amount > 0 and click Make Payment from the actions menu. The payment form opens pre-filled with the supplier, amount, and invoice reference.
2. Standalone Payment: Navigate to Payments in the sidebar, click ＋ New, and:
   • Set Payment Type to Pay.
   • Select the Supplier.
   • Add one or more Purchase Invoice references in the Payment Reference table.
   • Set the Amount (auto-calculated from references).
   • Select the Payment Method.
   • Click Save then Submit.
3. Auto Payment: On the Purchase Invoice, enable Make Payment On Submit in the Settings tab. When you submit the invoice, a payment is automatically created and submitted using the default payment account.

List View

The Payment list displays:

5.3 Supplier Management

Suppliers in NkapBooks are managed as Party records with the role set to Supplier (or Both for parties that are both customers and suppliers). Supplier records store contact information, default billing accounts, and track outstanding balances.

Schema Overview

Default Account Logic

The default payables account is automatically set based on the supplier's role and the company's country:

The system checks for account existence in the order listed and assigns the first available account.

Outstanding Amount Calculation

The supplier's outstanding amount is automatically recalculated whenever:

• A Purchase Invoice is submitted or cancelled.
• A Payment is submitted or cancelled.

The calculation sums the outstandingAmount field of all submitted, non-cancelled Purchase Invoices for the supplier.

Actions

The following actions are available from a Supplier record:

List View

The Supplier list displays:

Workflow: Creating a Supplier

1. Navigate to Purchases → Suppliers in the sidebar (or Party list filtered by role).
2. Click ＋ New to create a new supplier.
3. Enter the Name and set the Role to Supplier.
4. Fill in contact details: Email, Phone, and Address.
5. Optionally set the Tax ID, Currency, and Default Account.
6. If migrating from another system, enter the Opening Balance.
7. Click Save.

5.4 Purchase Items

Items for purchase are managed through the same Item document type used for sales, but with the for field set to Purchases or Both. Purchase items define the products and services your business buys from suppliers.

Schema Overview

Expense Account Logic

The expense account for purchase items is automatically determined based on multiple factors:

Validations

The Item model enforces the following validations:

Read-Only After Save

The following fields become read-only after the item is first saved to prevent data integrity issues:

• Unit — Changing the base unit would invalidate existing transactions.
• Item Type — Switching between Product and Service would affect account mappings.
• Track Item — Enabling/disabling inventory tracking after transactions exist would cause inconsistencies.
• Has Batch — Batch tracking cannot be toggled after initial configuration.
• Has Serial Number — Serial number tracking cannot be toggled after initial configuration.

Actions

The following actions are available from a purchase Item record:

List View

The Item list displays:

Workflow: Creating a Purchase Item

1. Navigate to Items in the sidebar.
2. Click ＋ New to create a new item.
3. Enter the Item Name.
4. Set Item Type to Product or Service.
5. Set For to Purchases or Both.
6. Enter the Purchase Rate (default cost).
7. Select the Unit of measurement.
8. Optionally assign a Tax template.
9. For inventory-tracked products:
   • Check Track Item to enable stock tracking.
   • Optionally enable Has Batch for batch tracking.
   • Optionally enable Has Serial Number for individual unit tracking.
10. Click Save.

Purchase Module Integration Map

The Purchase Module integrates tightly with other NkapBooks modules:

┌──────────────┐     creates      ┌─────────────────┐
│   Supplier   │────────────────▶│ Purchase Invoice │
│   (Party)    │                  │    (PINV-)       │
└──────────────┘                  └────────┬─────────┘
                                           │
                          ┌────────────────┼────────────────┐
                          │                │                │
                          ▼                ▼                ▼
                   ┌─────────────┐  ┌────────────┐  ┌──────────────┐
                   │   Payment   │  │  Purchase   │  │   Return     │
                   │   (PAY-)    │  │  Receipt    │  │  (Debit Note)│
                   │             │  │  (PREC-)    │  │  (PINV-)     │
                   └─────────────┘  └──────┬─────┘  └──────────────┘
                                           │
                                           ▼
                                    ┌─────────────┐
                                    │   Stock     │
                                    │   Ledger    │
                                    │   Entries   │
                                    └─────────────┘

Best Practices

Invoice Management

• Always verify supplier details before submitting a purchase invoice. Once submitted, the invoice cannot be edited — only cancelled and re-created.
• Use auto-payment for cash purchases where payment is made immediately upon receiving the bill.
• Use auto-receipt for inventory items to ensure stock levels are updated simultaneously with the accounting entries.
• Attach source documents — Upload the original vendor bill as an attachment to maintain an audit trail.

Supplier Management

• Set default currencies for international suppliers to ensure correct exchange rate handling on every invoice.
• Use the "Both" role for parties that are both customers and suppliers to maintain a single consolidated record with net outstanding tracking.
• Monitor outstanding amounts regularly by reviewing the supplier list or running the General Ledger report filtered by the payables account.

Item Management

• Enable inventory tracking for all physical goods you want to track in stock. This ensures that purchase invoices and receipts update your stock levels.
• Set accurate purchase rates — These serve as defaults when creating purchase invoices and are automatically synced with the Moving Average valuation rate when that valuation method is active.
• Use "Both" for dual-purpose items — Items sold and purchased should have for set to Both so they appear in both sales and purchase invoice item selectors.