diff --git a/models/doctype/PurchaseInvoice/PurchaseInvoice.js b/models/doctype/PurchaseInvoice/PurchaseInvoice.js
index 957c7d64..bf1c447d 100644
--- a/models/doctype/PurchaseInvoice/PurchaseInvoice.js
+++ b/models/doctype/PurchaseInvoice/PurchaseInvoice.js
@@ -1,5 +1,5 @@
-import { getActions } from '../Transaction/Transaction';
 import InvoiceTemplate from '../SalesInvoice/InvoiceTemplate.vue';
+import { getActions } from '../Transaction/Transaction';
 import PurchaseInvoice from './PurchaseInvoiceDocument';
 
 export default {
@@ -61,7 +61,8 @@ export default {
       fieldname: 'exchangeRate',
       label: 'Exchange Rate',
       fieldtype: 'Float',
-      formula: (doc) => doc.getExchangeRate(),
+      default: 1,
+      formula: async (doc) => await doc.getExchangeRate(),
       required: true,
     },
     {
@@ -75,7 +76,7 @@ export default {
       fieldname: 'netTotal',
       label: 'Net Total',
       fieldtype: 'Currency',
-      formula: (doc) => doc.getSum('items', 'amount'),
+      formula: (doc) => doc.getSum('items', 'amount', false),
       readOnly: 1,
       getCurrency: (doc) => doc.currency,
     },
@@ -83,7 +84,7 @@ export default {
       fieldname: 'baseNetTotal',
       label: 'Net Total (Company Currency)',
       fieldtype: 'Currency',
-      formula: (doc) => doc.netTotal * doc.exchangeRate,
+      formula: (doc) => doc.netTotal.mul(doc.exchangeRate),
       readOnly: 1,
     },
     {
@@ -106,7 +107,7 @@ export default {
       fieldname: 'baseGrandTotal',
       label: 'Grand Total (Company Currency)',
       fieldtype: 'Currency',
-      formula: (doc) => doc.grandTotal * doc.exchangeRate,
+      formula: (doc) => doc.grandTotal.mul(doc.exchangeRate),
       readOnly: 1,
     },
     {
diff --git a/models/doctype/PurchaseInvoiceItem/PurchaseInvoiceItem.js b/models/doctype/PurchaseInvoiceItem/PurchaseInvoiceItem.js
index 35f8eef0..dfa031e9 100644
--- a/models/doctype/PurchaseInvoiceItem/PurchaseInvoiceItem.js
+++ b/models/doctype/PurchaseInvoiceItem/PurchaseInvoiceItem.js
@@ -32,7 +32,7 @@ export default {
       label: 'Quantity',
       fieldtype: 'Float',
       required: 1,
-      formula: () => 1,
+      default: 1,
     },
     {
       fieldname: 'rate',
@@ -40,9 +40,9 @@ export default {
       fieldtype: 'Currency',
       required: 1,
       formula: async (row, doc) => {
-        const baseRate = (await doc.getFrom('Item', row.item, 'rate')) || 0;
-        const exchangeRate = doc.exchangeRate ?? 1;
-        return baseRate / exchangeRate;
+        const baseRate =
+          (await doc.getFrom('Item', row.item, 'rate')) || frappe.pesa(0);
+        return baseRate.div(doc.exchangeRate);
       },
       getCurrency: (row, doc) => doc.currency,
     },
@@ -50,7 +50,7 @@ export default {
       fieldname: 'baseRate',
       label: 'Rate (Company Currency)',
       fieldtype: 'Currency',
-      formula: (row, doc) => row.rate * doc.exchangeRate,
+      formula: (row, doc) => row.rate.mul(doc.exchangeRate),
       readOnly: 1,
     },
     {
@@ -76,7 +76,7 @@ export default {
       label: 'Amount',
       fieldtype: 'Currency',
       readOnly: 1,
-      formula: (row) => row.quantity * row.rate,
+      formula: (row) => row.rate.mul(row.quantity),
       getCurrency: (row, doc) => doc.currency,
     },
     {
@@ -84,7 +84,7 @@ export default {
       label: 'Amount (Company Currency)',
       fieldtype: 'Currency',
       readOnly: 1,
-      formula: (row, doc) => row.amount * doc.exchangeRate,
+      formula: (row, doc) => row.amount.mul(doc.exchangeRate),
     },
   ],
 };
diff --git a/models/doctype/TaxSummary/TaxSummary.js b/models/doctype/TaxSummary/TaxSummary.js
index f5d1f7ba..dc130167 100644
--- a/models/doctype/TaxSummary/TaxSummary.js
+++ b/models/doctype/TaxSummary/TaxSummary.js
@@ -8,26 +8,26 @@ export default {
       label: 'Tax Account',
       fieldtype: 'Link',
       target: 'Account',
-      required: 1
+      required: 1,
     },
     {
       fieldname: 'rate',
       label: 'Rate',
       fieldtype: 'Float',
-      required: 1
+      required: 1,
     },
     {
       fieldname: 'amount',
       label: 'Amount',
       fieldtype: 'Currency',
-      required: 1
+      required: 1,
     },
     {
       fieldname: 'baseAmount',
       label: 'Amount (Company Currency)',
       fieldtype: 'Currency',
-      formula: (row, doc) => row.amount * doc.exchangeRate,
-      readOnly: 1
-    }
-  ]
+      formula: (row, doc) => row.amount.mul(doc.exchangeRate),
+      readOnly: 1,
+    },
+  ],
 };
diff --git a/models/doctype/Transaction/TransactionDocument.js b/models/doctype/Transaction/TransactionDocument.js
index f4fa7bfa..3fc7747a 100644
--- a/models/doctype/Transaction/TransactionDocument.js
+++ b/models/doctype/Transaction/TransactionDocument.js
@@ -1,11 +1,10 @@
-import BaseDocument from 'frappejs/model/document';
 import frappe from 'frappejs';
-import { round } from 'frappejs/utils/numberFormat';
+import BaseDocument from 'frappejs/model/document';
 import { getExchangeRate } from '../../../accounting/exchangeRate';
 
 export default class TransactionDocument extends BaseDocument {
   async getExchangeRate() {
-    if (!this.currency) return;
+    if (!this.currency) return 1.0;
 
     let accountingSettings = await frappe.getSingle('AccountingSettings');
     const companyCurrency = accountingSettings.currency;
@@ -14,7 +13,7 @@ export default class TransactionDocument extends BaseDocument {
     }
     return await getExchangeRate({
       fromCurrency: this.currency,
-      toCurrency: companyCurrency
+      toCurrency: companyCurrency,
     });
   }
 
@@ -22,31 +21,30 @@ export default class TransactionDocument extends BaseDocument {
     let taxes = {};
 
     for (let row of this.items) {
-      if (row.tax) {
-        let tax = await this.getTax(row.tax);
-        for (let d of tax.details) {
-          let amount = (row.amount * d.rate) / 100;
-          taxes[d.account] = taxes[d.account] || {
-            account: d.account,
-            rate: d.rate,
-            amount: 0
-          };
-          // collect amount
-          taxes[d.account].amount += amount;
-        }
+      if (!row.tax) {
+        continue;
+      }
+
+      const tax = await this.getTax(row.tax);
+      for (let d of tax.details) {
+        taxes[d.account] = taxes[d.account] || {
+          account: d.account,
+          rate: d.rate,
+          amount: frappe.pesa(0),
+        };
+
+        const amount = row.amount.mul(d.rate).div(100);
+        taxes[d.account].amount = taxes[d.account].amount.add(amount);
       }
     }
 
-    return (
-      Object.keys(taxes)
-        .map(account => {
-          let tax = taxes[account];
-          tax.baseAmount = round(tax.amount * this.exchangeRate, 2);
-          return tax;
-        })
-        // clear rows with 0 amount
-        .filter(tax => tax.amount)
-    );
+    return Object.keys(taxes)
+      .map((account) => {
+        const tax = taxes[account];
+        tax.baseAmount = tax.amount.mul(this.exchangeRate);
+        return tax;
+      })
+      .filter((tax) => !tax.amount.isZero());
   }
 
   async getTax(tax) {
@@ -56,13 +54,8 @@ export default class TransactionDocument extends BaseDocument {
   }
 
   async getGrandTotal() {
-    let grandTotal = this.netTotal;
-    if (this.taxes) {
-      for (let row of this.taxes) {
-        grandTotal += row.amount;
-      }
-    }
-
-    return grandTotal;
+    return (this.taxes || [])
+      .map(({ amount }) => amount)
+      .reduce((a, b) => a.add(b), this.netTotal);
   }
-};
+}