diff --git a/app/components/Form/PayForm.js b/app/components/Form/PayForm.js
index 4a1edc8f..3d93da5f 100644
--- a/app/components/Form/PayForm.js
+++ b/app/components/Form/PayForm.js
@@ -21,7 +21,7 @@ class PayForm extends Component {
 
   render() {
     const {
-      payform: { amount, payInput },
+      payform: { amount, payInput, showErrors },
       currency,
       crypto,
 
@@ -30,9 +30,13 @@ class PayForm extends Component {
       currentAmount,
       inputCaption,
       showPayLoadingScreen,
+      payFormIsValid: { errors, isValid },
 
       setPayAmount,
+      onPayAmountBlur,
+
       setPayInput,
+      onPayInputBlur,
 
       onPaySubmit
     } = this.props
@@ -41,7 +45,12 @@ class PayForm extends Component {
       <div className={styles.container}>
         {showPayLoadingScreen && <LoadingBolt />}
 
-        <section className={`${styles.amountContainer} ${isLn ? styles.ln : ''}`}>
+        <section className={`${styles.amountContainer} ${isLn ? styles.ln : ''} ${showErrors.amount && styles.error}`}>
+          <section className={`${styles.amountError} ${showErrors.amount && styles.active}`}>
+            {showErrors.amount &&
+              <span>{errors.amount}</span>
+            }
+          </section>
           <label htmlFor='amount'>
             <CurrencyIcon currency={currency} crypto={crypto} />
           </label>
@@ -58,6 +67,7 @@ class PayForm extends Component {
             }
             value={currentAmount}
             onChange={event => setPayAmount(event.target.value)}
+            onBlur={onPayAmountBlur}
             id='amount'
             readOnly={isLn}
           />
@@ -80,18 +90,24 @@ class PayForm extends Component {
               </i>
             }
           </aside>
-          <section className={styles.input}>
+          <section className={`${styles.input} ${showErrors.payInput && styles.error}`}>
             <input
               type='text'
               placeholder='Payment request or bitcoin address'
               value={payInput}
               onChange={event => setPayInput(event.target.value)}
+              onBlur={onPayInputBlur}
               id='paymentRequest'
             />
           </section>
+          <section className={`${styles.payInputError} ${showErrors.payInput && styles.active}`}>
+            {showErrors.payInput &&
+              <span>{errors.payInput}</span>
+            }
+          </section>
         </div>
         <section className={styles.buttonGroup}>
-          <div className={styles.button} onClick={onPaySubmit}>Pay</div>
+          <div className={`${styles.button} ${isValid && styles.active}`} onClick={onPaySubmit}>Pay</div>
         </section>
       </div>
     )
@@ -112,9 +128,12 @@ PayForm.propTypes = {
   ]).isRequired,
   inputCaption: PropTypes.string.isRequired,
   showPayLoadingScreen: PropTypes.bool.isRequired,
+  payFormIsValid: PropTypes.object.isRequired,
 
   setPayAmount: PropTypes.func.isRequired,
+  onPayAmountBlur: PropTypes.func.isRequired,
   setPayInput: PropTypes.func.isRequired,
+  onPayInputBlur: PropTypes.func.isRequired,
   fetchInvoice: PropTypes.func.isRequired,
 
   onPaySubmit: PropTypes.func.isRequired
diff --git a/app/components/Form/PayForm.scss b/app/components/Form/PayForm.scss
index d50710ad..572434c8 100644
--- a/app/components/Form/PayForm.scss
+++ b/app/components/Form/PayForm.scss
@@ -10,16 +10,35 @@
 }
 
 .amountContainer {
+  position: relative;
   color: $main;
   display: flex;
   justify-content: center;
   min-height: 120px;
   margin-bottom: 20px;
   min-height: 175px;
+  border-bottom: 1px solid transparent;
 
   &.ln {
     opacity: 0.75;
   }
+
+  &.error {
+    border-color: $red; 
+  }
+
+  .amountError {
+    position: absolute;
+    top: 0;
+    right: 0;
+    opacity: 0;
+    color: $red;
+    transition: all 0.25s ease;
+
+    &.active {
+      opacity: 1;
+    }
+  }
   
   label, input[type=number], input[type=text] {
     color: inherit;
@@ -92,6 +111,10 @@
   position: relative;
   padding: 0 20px;
 
+  &.error {
+    border-color: $red;
+  }
+
   label, input[type=number], input[type=text] {
     font-size: inherit;
   }
@@ -112,6 +135,18 @@
   }
 }
 
+.payInputError {
+  margin: 10px 0;
+  min-height: 20px;
+  color: $red;
+  opacity: 0;
+  transition: all 0.25s ease;
+
+  &.active {
+    opacity: 1;
+  }
+}
+
 .buttonGroup {
   width: 100%;
   display: flex;
@@ -120,7 +155,6 @@
   overflow: hidden;
 
   .button {
-    cursor: pointer;
     height: 55px;
     min-height: 55px;
     text-transform: none;
@@ -134,9 +168,16 @@
     width: 100%;
     text-align: center;
     line-height: 55px;
+    opacity: 0.5;
+    cursor: default;
 
     &:first-child {
       border-right: 1px solid lighten($main, 20%);
     }
+
+    &.active {
+      opacity: 1;
+      cursor: pointer;
+    }
   }
 }
\ No newline at end of file
diff --git a/app/reducers/payform.js b/app/reducers/payform.js
index b7e8bcbe..b031b8ff 100644
--- a/app/reducers/payform.js
+++ b/app/reducers/payform.js
@@ -1,5 +1,8 @@
 import { createSelector } from 'reselect'
 import bitcoin from 'bitcoinjs-lib'
+
+import isEmpty from 'lodash/isEmpty'
+
 import { tickerSelectors } from './ticker'
 import { btc, bech32 } from '../utils'
 
@@ -12,6 +15,11 @@ const initialState = {
     payreq: '',
     r_hash: '',
     amount: '0'
+  },
+
+  showErrors: {
+    amount: false,
+    payInput: false
   }
 }
 
@@ -21,6 +29,8 @@ export const SET_PAY_AMOUNT = 'SET_PAY_AMOUNT'
 export const SET_PAY_INPUT = 'SET_PAY_INPUT'
 export const SET_PAY_INVOICE = 'SET_PAY_INVOICE'
 
+export const UPDATE_PAY_ERRORS = 'UPDATE_PAY_ERRORS'
+
 export const RESET_FORM = 'RESET_FORM'
 
 // ------------------------------------
@@ -47,9 +57,10 @@ export function setPayInvoice(invoice) {
   }
 }
 
-export function resetPayForm() {
+export function updatePayErrors(errorsObject) {
   return {
-    type: RESET_FORM
+    type: UPDATE_PAY_ERRORS,
+    errorsObject
   }
 }
 
@@ -57,9 +68,11 @@ export function resetPayForm() {
 // Action Handlers
 // ------------------------------------
 const ACTION_HANDLERS = {
-  [SET_PAY_AMOUNT]: (state, { amount }) => ({ ...state, amount }),
-  [SET_PAY_INPUT]: (state, { payInput }) => ({ ...state, payInput }),
-  [SET_PAY_INVOICE]: (state, { invoice }) => ({ ...state, invoice }),
+  [SET_PAY_AMOUNT]: (state, { amount }) => ({ ...state, amount, showErrors: Object.assign(state.showErrors, { amount: false }) }),
+  [SET_PAY_INPUT]: (state, { payInput }) => ({ ...state, payInput, showErrors: Object.assign(state.showErrors, { payInput: false }) }),
+  [SET_PAY_INVOICE]: (state, { invoice }) => ({ ...state, invoice, showErrors: Object.assign(state.showErrors, { amount: false }) }),
+
+  [UPDATE_PAY_ERRORS]: (state, { errorsObject }) => ({ ...state, showErrors: Object.assign(state.showErrors, errorsObject) }),
 
   [RESET_FORM]: () => (initialState)
 }
@@ -75,7 +88,7 @@ const payInvoiceSelector = state => state.payform.invoice
 // transaction
 const sendingTransactionSelector = state => state.transaction.sendingTransaction
 
-// transaction
+// payment
 const sendingPaymentSelector = state => state.payment.sendingPayment
 
 // ticker
@@ -84,7 +97,6 @@ const currencySelector = state => state.ticker.currency
 payFormSelectors.isOnchain = createSelector(
   payInputSelector,
   (input) => {
-    // TODO: work with bitcoin-js to fix p2wkh error and make testnet/mainnet dynamic
     try {
       bitcoin.address.toOutputScript(input, bitcoin.networks.testnet)
       return true
@@ -149,6 +161,30 @@ payFormSelectors.showPayLoadingScreen = createSelector(
   (sendingTransaction, sendingPayment) => sendingTransaction || sendingPayment
 )
 
+payFormSelectors.payFormIsValid = createSelector(
+  payFormSelectors.isOnchain,
+  payFormSelectors.isLn,
+  payAmountSelector,
+  (isOnchain, isLn, amount) => {
+    const errors = {}
+
+    if (!isLn && amount <= 0) {
+      errors.amount = 'Amount must be more than 0'
+    }
+
+    if (!isOnchain && !isLn) {
+      errors.payInput = 'Must be a valid BTC address or Lightning Network request'
+    }
+
+    return {
+      errors,
+      amountIsValid: isEmpty(errors.amount),
+      payInputIsValid: isEmpty(errors.payInput),
+      isValid: isEmpty(errors)
+    }
+  }
+)
+
 export { payFormSelectors }
 
 // ------------------------------------
diff --git a/app/routes/app/containers/AppContainer.js b/app/routes/app/containers/AppContainer.js
index 17782a5a..7da0a72b 100644
--- a/app/routes/app/containers/AppContainer.js
+++ b/app/routes/app/containers/AppContainer.js
@@ -7,7 +7,7 @@ import { fetchInfo } from 'reducers/info'
 import { showModal, hideModal } from 'reducers/modal'
 
 import { setFormType } from 'reducers/form'
-import { setPayAmount, setPayInput, payFormSelectors } from 'reducers/payform'
+import { setPayAmount, setPayInput, updatePayErrors, payFormSelectors } from 'reducers/payform'
 import { setRequestAmount, setRequestMemo } from 'reducers/requestform'
 
 import { sendCoins } from 'reducers/transaction'
@@ -31,6 +31,8 @@ const mapDispatchToProps = {
 
   setPayAmount,
   setPayInput,
+  updatePayErrors,
+
   setRequestAmount,
   setRequestMemo,
 
@@ -59,7 +61,8 @@ const mapStateToProps = state => ({
   isLn: payFormSelectors.isLn(state),
   currentAmount: payFormSelectors.currentAmount(state),
   inputCaption: payFormSelectors.inputCaption(state),
-  showPayLoadingScreen: payFormSelectors.showPayLoadingScreen(state)
+  showPayLoadingScreen: payFormSelectors.showPayLoadingScreen(state),
+  payFormIsValid: payFormSelectors.payFormIsValid(state)
 })
 
 const mergeProps = (stateProps, dispatchProps, ownProps) => {
@@ -73,14 +76,45 @@ const mergeProps = (stateProps, dispatchProps, ownProps) => {
     currentAmount: stateProps.currentAmount,
     inputCaption: stateProps.inputCaption,
     showPayLoadingScreen: stateProps.showPayLoadingScreen,
+    payFormIsValid: stateProps.payFormIsValid,
 
     setPayAmount: dispatchProps.setPayAmount,
     setPayInput: dispatchProps.setPayInput,
     fetchInvoice: dispatchProps.fetchInvoice,
 
+    onPayAmountBlur: () => {
+      // If the amount is now valid and showErrors was on, turn it off
+      if (stateProps.payFormIsValid.amountIsValid && stateProps.payform.showErrors.amount) {
+        dispatchProps.updatePayErrors({ amount: false })
+      }
+
+      // If the amount is not valid and showErrors was off, turn it on
+      if (!stateProps.payFormIsValid.amountIsValid && !stateProps.payform.showErrors.amount) {
+        dispatchProps.updatePayErrors({ amount: true })
+      }
+    },
+
+    onPayInputBlur: () => {
+      // If the input is now valid and showErrors was on, turn it off
+      if (stateProps.payFormIsValid.payInputIsValid && stateProps.payform.showErrors.payInput) {
+        dispatchProps.updatePayErrors({ payInput: false })
+      }
+
+      // If the input is not valid and showErrors was off, turn it on
+      if (!stateProps.payFormIsValid.payInputIsValid && !stateProps.payform.showErrors.payInput) {
+        dispatchProps.updatePayErrors({ payInput: true })
+      }
+    },
 
     onPaySubmit: () => {
-      if (!stateProps.isOnchain && !stateProps.isLn) { return }
+      if (!stateProps.payFormIsValid.isValid) {
+        dispatchProps.updatePayErrors({
+          amount: Object.prototype.hasOwnProperty.call(stateProps.payFormIsValid.errors, 'amount'),
+          payInput: Object.prototype.hasOwnProperty.call(stateProps.payFormIsValid.errors, 'payInput')
+        })
+
+        return
+      }
 
       if (stateProps.isOnchain) {
         dispatchProps.sendCoins({
diff --git a/package.json b/package.json
index fdf4f4c3..846a1e6a 100644
--- a/package.json
+++ b/package.json
@@ -195,6 +195,7 @@
     "font-awesome": "^4.7.0",
     "grpc": "^1.4.1",
     "history": "^4.6.3",
+    "lodash": "^4.17.4",
     "moment-timezone": "^0.5.13",
     "prop-types": "^15.5.10",
     "qrcode.react": "^0.7.1",
diff --git a/test/components/Form.spec.js b/test/components/Form.spec.js
index 3024a3b4..d90556ff 100644
--- a/test/components/Form.spec.js
+++ b/test/components/Form.spec.js
@@ -15,9 +15,12 @@ const payFormProps = {
   currentAmount: '0',
   inputCaption: '',
   showPayLoadingScreen: false,
+  payFormIsValid: {},
 
   setPayAmount: () => {},
+  onPayAmountBlur: () => {},
   setPayInput: () => {},
+  onPayInputBlur: () => {},
   fetchInvoice: () => {},