ERP Documentation - Purchase Module

Module Relationship Diagram (ERD)

        erDiagram
            SUPPLIER_CATEGORIES ||--|{ SUPPLIERS : "categorizes"
            SUPPLIERS ||--|{ ITEM_PURCHASE_PRICES : "sets"
            SUPPLIERS ||--|{ PURCHASE_ORDERS : "receives"
            
            PURCHASE_ORDERS ||--|{ PURCHASE_ORDER_ITEMS : "contains"
            %% PURCHASE_ORDER_ITEMS ||--|{ PURCHASE_SCHEDULE_ITEMS : "has"  %% (schedule items commented out)

            PURCHASE_INVOICES ||--|{ PURCHASE_INVOICE_ITEMS : "contains"
            PURCHASE_INVOICES }o--|| SUPPLIER_PAYMENTS : "is paid by"

            PURCHASE_RETURNS ||--|{ PURCHASE_RETURN_ITEMS : "contains"

            SUPPLIER_CATEGORIES {
                int id PK
                string category_name
                string description
                bool is_active
            }

            SUPPLIERS {
                int id PK
                int supplier_category_id FK
                int branch_id FK
                int general_ledger_account_id FK "Accounts Payable"
                int purchase_general_ledger_account_id FK "Purchase Account"
                int purchase_discount_ledger_account_id FK "Purchase Discount Account"
                int advance_tax_ledger_account_id FK "Advance Tax Account"
                string supplier_code
                string supplier_name
                string address
                string residential_phone
                string office_phone
                string relevant_person
                string mobile_number
                string email
                string saletax_reg_no
                string payment_term
                int credit_days
                decimal credit_limit
                bool is_active
            }


            ITEM_PURCHASE_PRICES {
                int id PK
                int item_variant_id FK
                int supplier_id FK
                decimal purchase_price
                decimal purchase_discount
                datetime effective_date
            }

            PURCHASE_ORDERS {
                int id PK
                int supplier_id FK
                int branch_id FK
                string po_number "Unique PO code"
                date order_date
                date delivery_date
                string purchaser "Employee/User who created"
                string payment_term "Net 30, COD, etc."
                string trade_term "FOB, CIF, etc."
                decimal sub_total
                decimal total_discount
                decimal tax_amount
                decimal net_total
                string status "draft, approved, closed, cancelled"
                text remarks
                datetime created_at
                datetime updated_at
            }

        PURCHASE_ORDER_ITEMS {
            int id PK
            int purchase_order_id FK
            int item_variant_id FK
            decimal quantity
            decimal unit_price
            decimal discount
            json tax "[{tax_id: 1, tax_name: VAT}, {tax_id: 2, tax_name: 'Service Tax'}]"
            int total_tax_amount "Sum of all taxes applied"
            decimal line_total
        }

        %% PURCHASE_SCHEDULE_ITEMS {                        %% (Deprecated/commented in ERD)
        %%     int id PK
        %%     int purchase_order_item_id FK
        %%     date schedule_date
        %%     decimal scheduled_qty
        %%     string status "pending, delivered, cancelled"
        %% }

        SUPPLIERS ||--|{ SUPPLIER_ADVANCES : "receives"
        SUPPLIER_ADVANCES ||--|{ SUPPLIER_ADVANCE_ALLOCATIONS : "is allocated to"
        SUPPLIER_ADVANCE_ALLOCATIONS }o--|| PURCHASE_INVOICES : "applies to"

        SUPPLIER_ADVANCES {
    int id PK
    int supplier_id FK
    string advance_code "e.g., ADV-2026-001"
    
    decimal total_amount
    decimal available_balance
    
    string status "draft, active, exhausted, closed"

    enum payment_method "CASH|BANK_TRANSFER"
    
    int voucher_id FK           "The GL Journal Entry for the Payment"
    string description          "e.g., Advance for Project Alpha raw materials"
            
    datetime closed_at
    string closed_reason        "e.g., Project cancelled"
    
    datetime created_at
    int created_by FK
}

        SUPPLIER_ADVANCE_ALLOCATIONS {
    int id PK
    int supplier_advance_id FK
      
    enum allocation_type "DOWN_PAYMENT|INVOICE_PAYMENT"
    int reference_id FK         "The PO ID or Invoice ID"
    
    decimal amount
    
    
    int gl_voucher_id FK        "The Journal Entry created for THIS specific usage"
    
    
    string status "active, reversed" 
    
    datetime allocation_date
    int created_by FK
    text note                   "e.g., Used against INV-101"
    
    datetime created_at
}

        PURCHASE_INVOICES {
            int id PK
            string invoice_number
            date invoice_date
            decimal sub_total
            decimal total_discount
            decimal shipping_cost
            decimal tax_amount
            decimal net_total
            string reference_type "PO, GRN, Others"
            int reference_id FK "ID of linked PO or GRN"
            string status "unpaid, partially_paid, paid, cancelled"
            datetime posted_at "When invoice was finalized"
        }

        PURCHASE_INVOICE_ITEMS {
            int id PK
            int purchase_invoice_id FK
            int item_variant_id FK
            decimal quantity
            decimal unit_price
            decimal discount
            json tax "[{tax_id: 1, tax_name: VAT}, {tax_id: 2, tax_name: 'Service Tax'}]"
            int total_tax_amount "Sum of all taxes applied"
            decimal line_total
        }

        SUPPLIER_PAYMENTS {
            int id PK
            int invoice_id FK
            decimal amount
            date payment_date
            string payment_method "Cash, Bank Transfer, Cheque"
            string reference_number
            string status "pending, cleared, bounced"
        }

       PURCHASE_RETURN_INVOICE {
        bigint id PK
        varchar return_number UK
        bigint purchase_invoice_id FK
        bigint receiving_return_voucher_id FK
        bigint supplier_id FK
        bigint branch_id FK
        date return_date
        varchar return_reason
        decimal sub_total
        decimal total_discount
        decimal tax_amount
        decimal total_amount
        enum status
        timestamp posted_at
        text remarks
        bigint created_by FK
    }
    PURCHASE_RETURN_INVOICE_items {
        bigint id PK
        bigint purchase_return_invoice_id FK
        bigint item_variant_id FK
        decimal quantity
        decimal unit_price
        decimal discount
        json tax
        decimal total_tax_amount
        decimal line_total
    }

Purchase Module - Main Flow

                        flowchart LR
                            %% Main Flow Controller
                            S1[1. Supplier
Setup]:::setup --> S2[2. Purchase
Order]:::procurement
                            S2 --> S3[3. Purchase
Invoice]:::receiving
                            S3 --> S4[4. Supplier
Payment]:::financials
                            S3 -.-> S5[5. Purchase
Return]:::returns
                            S4 & S5 & S3 -.-> S6[6. Financial
Posting]:::gl

                            %% Styles
                            classDef setup fill:#262f4a,stroke:#58648c,color:#fff
                            classDef procurement fill:#3a244a,stroke:#7e529e,color:#fff
                            classDef receiving fill:#1e4348,stroke:#428a94,color:#fff
                            classDef financials fill:#244a44,stroke:#529e94,color:#fff
                            classDef returns fill:#4a2424,stroke:#9e5252,color:#fff
                            classDef gl fill:#4a4424,stroke:#9e9452,color:#fff
                            classDef reporting fill:#243a4a,stroke:#527e9e,color:#fff

1. Supplier Setup Flow

                    flowchart LR
                        A1[Create Supplier Category] --> A2[Add Supplier Details & Link Accounts]
                        A2 --> A3{Has Opening Balance?}
                        A3 -- Yes --> A4[Enter Opening Balance
Cr: Accounts Payable]
                        A3 -- No --> A5[Optional: Set Supplier-Item Prices]
                        A4 --> A5
                        A5 --> A_END(( Ready))

                        %% Styles
                        classDef setup fill:#262f4a,stroke:#58648c,color:#fff
                        class A1,A2,A3,A4,A5,A_END setup

2. Purchase Order (PO) Flow

                    flowchart LR
                        B1[Create Purchase Order
Status: Draft] --> B2[Add PO Items]
                        B2 --> B3{Options?}
                        B3 -- Add Schedules --> B4[Define Delivery Schedules]
                        B3 -- Add Downpayment --> B5[Record Downpayment
Dr: Supplier Advance
Cr: Bank]
                        B3 -- Approve --> B6[Approve PO
Status: Approved]
                        B4 --> B6
                        B5 --> B6
                        B6 --> B_END(( Contractual Stage))

                        %% Styles
                        classDef procurement fill:#3a244a,stroke:#7e529e,color:#fff
                        class B1,B2,B3,B4,B5,B6,B_END procurement

3. Purchase Invoice Flow

                    flowchart LR
                        C1[Create Invoice & Link to PO] --> C2[Add Items & Match to PO/GRN]
                        C2 --> C3{Downpayment to apply?}
                        C3 -- Yes --> C4[Adjust Downpayment
Dr: Accts Payable
Cr: Supplier Advance]
                        C3 -- No --> C5[Post Invoice
Dr: Inventory/Expense
Cr: Accts Payable]
                        C4 --> C5
                        C5 --> C6[ Stock Levels Updated
Txn: Purchase In]
                        C6 --> C_END(( Liability Recorded))

                        %% Styles
                        classDef receiving fill:#1e4348,stroke:#428a94,color:#fff
                        class C1,C2,C3,C4,C5,C6,C_END receiving

4. Supplier Payment Flow

                    flowchart LR
                        D1[Create Payment & Select Invoices] --> D2{Method?}
                        D2 -- Cheque/Bank --> D3[Process Payment
Status: Pending -> Cleared]
                        D2 -- Cash --> D4[Payment Cleared Instantly]
                        D3 --> D5[Post Payment
Dr: Accts Payable
Cr: Bank/Cash]
                        D4 --> D5
                        D5 --> D_END(( Invoice Settled))

                        %% Styles
                        classDef financials fill:#244a44,stroke:#529e94,color:#fff
                        class D1,D2,D3,D4,D5,D_END financials

5. Purchase Return Flow

                    flowchart LR
                        E1[Create Return Against Invoice] --> E2[Add Return Items & Reason]
                        E2 --> E3[Post Return
Dr: Accts Payable
Cr: Inventory]
                        E3 --> E4[ Stock Levels Updated
Txn: Purchase Return]
                        E4 --> E_END(( Debit Note Created))

                        %% Styles
                        classDef returns fill:#4a2424,stroke:#9e5252,color:#fff
                        class E1,E2,E3,E4,E_END returns

6. Financial Posting Summary

                    graph TD
                        F1["PO Downpayment:
Dr: Supplier Advance
Cr: Bank"]
                        F2["Purchase Invoice:
Dr: Inventory
Cr: Accts Payable"]
                        F3["Downpayment Adjustment:
Dr: Accts Payable
Cr: Supplier Advance"]
                        F4["Supplier Payment:
Dr: Accts Payable
Cr: Bank"]
                        F5["Purchase Return:
Dr: Accts Payable
Cr: Inventory"]
                        
                        %% Styles
                        classDef gl fill:#4a4424,stroke:#9e9452,color:#fff
                        class F1,F2,F3,F4,F5 gl

7. Reporting & Analytics

                    graph TD
                        R1[Supplier Ledger & Aging]
                        R2[PO & Invoice Status Reports]
                        R3[Purchase & Return Analysis]
                        R4[Tax & Supplier Performance]

                        %% Styles
                        classDef reporting fill:#243a4a,stroke:#527e9e,color:#fff
                        class R1,R2,R3,R4 reporting

Table Documentation Links

Suppliers

Master data for all vendors, contacts, and pricing.

Purchase Orders (PO)

Requests for goods, including schedules and downpayments.

Purchase Invoices

The supplier's bill for goods; linked from a PO.

Supplier Payments

Records payments made against supplier invoices.

Purchase Returns

Manages returning goods to suppliers against an invoice.