ALTER TABLE IF EXISTS accounting.expenses
    ADD COLUMN IF NOT EXISTS tax_amount numeric(18, 2) NOT NULL DEFAULT 0,
    ADD COLUMN IF NOT EXISTS currency_code varchar(10) NOT NULL DEFAULT 'GHS',
    ADD COLUMN IF NOT EXISTS vendor_bill_id bigint,
    ADD COLUMN IF NOT EXISTS vendor_bill_no varchar(80);

CREATE INDEX IF NOT EXISTS idx_expenses_vendor_bill
    ON accounting.expenses (tenant_id, vendor_bill_id)
    WHERE vendor_bill_id IS NOT NULL;