diff --git a/src/app/components/forms/TextInputField/TextInputField.tsx b/src/app/components/forms/TextInputField/TextInputField.tsx
index 3aeeddc..e0d722a 100644
--- a/src/app/components/forms/TextInputField/TextInputField.tsx
+++ b/src/app/components/forms/TextInputField/TextInputField.tsx
@@ -1,14 +1,18 @@
 import type {
   FieldValues,
   RegisterOptions,
-  UseFormReturn
+  UseFormReturn,
+  FieldError,
+  ValidationValueMessage
 } from "react-hook-form"
 import {
+  ErrorMessage,
   Field,
   Label,
   TextInput,
   TextInputProps
 } from "@amsterdam/design-system-react"
+import { getValueByPath } from "app/utils/getValueByPath"
 
 type Props = {
   name: string
@@ -26,19 +30,37 @@ export const TextInputField: React.FC<Props> = ({
   formMethods = {},
   ...rest
 }) => {
-  const { formState, register } = formMethods as UseFormReturn<FieldValues>
-  const error = formState?.errors?.[name]
+  const { formState, register, setError, clearErrors, trigger, setValue } =
+    formMethods as UseFormReturn<FieldValues>
+  const error = getValueByPath(formState?.errors, name) as FieldError
   const hasError = !!error
 
+  const handleValidation = (e: React.ChangeEvent<HTMLInputElement>) => {
+    const value = e.target.value
+    setValue(name, value)
+    const pattern = validation?.pattern as ValidationValueMessage<RegExp>
+    const regex = pattern?.value
+    const message = pattern?.message || "Ongeldige invoer"
+    if (!value || !regex) return
+    if (regex.test(value)) {
+      clearErrors(name)
+    } else {
+      setError(name, { type: "custom", message })
+    }
+    void trigger()
+  }
+
   return (
     <Field>
       <Label htmlFor={name}>{label}</Label>
+      {hasError && <ErrorMessage>{error?.message}</ErrorMessage>}
       <TextInput
         id={name}
         invalid={hasError}
         type={type}
         {...(register ? register(name, validation) : {})}
         {...rest}
+        onChange={handleValidation}
       />
     </Field>
   )
diff --git a/src/app/pages/CaseCreatePage/CaseCreatePage.tsx b/src/app/pages/CaseCreatePage/CaseCreatePage.tsx
index ba73e75..7376ec1 100644
--- a/src/app/pages/CaseCreatePage/CaseCreatePage.tsx
+++ b/src/app/pages/CaseCreatePage/CaseCreatePage.tsx
@@ -66,7 +66,7 @@ export const CaseCreatePage: React.FC = () => {
       ) : (
         <Form
           onSubmit={onSubmit}
-          hasDummyButton={env.VITE_ENV === "LOCAL"}
+          hasDummyButton={env.VITE_ENV === "LOCAL" || env.VITE_ENV === "ONT"}
           dummyValues={defaultDummyValues}
         >
           <RadioGroupFieldSet
diff --git a/src/app/pages/CaseCreatePage/ContactsFormFields.tsx b/src/app/pages/CaseCreatePage/ContactsFormFields.tsx
index acc53ab..1a4e506 100644
--- a/src/app/pages/CaseCreatePage/ContactsFormFields.tsx
+++ b/src/app/pages/CaseCreatePage/ContactsFormFields.tsx
@@ -8,13 +8,21 @@ type Props = {
 }
 
 const emailValidation = {
-  required: "E-mail is verplicht",
+  required: true,
   pattern: {
     value: /^[a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+\.[a-zA-Z]{2,}$/,
     message: "Dit is geen geldig e-mailadres"
   }
 }
 
+const phoneValidation = {
+  required: true,
+  pattern: {
+    value: /^(0031|0)[1-9][0-9]{8,9}$/,
+    message: "Dit is geen geldig telefoonnummer"
+  }
+}
+
 const requiredValidation = { required: true }
 
 export const ContactsFormFields: React.FC<Props> = ({ formMethods }) => {
@@ -40,12 +48,12 @@ export const ContactsFormFields: React.FC<Props> = ({ formMethods }) => {
             validation={ emailValidation }
             formMethods={ formMethods }
           />
-          <Row wrap>
+          <Row wrap alignVertical="end">
             <TextInputField
               name={`phone[${ contact.id }]`}
               label="Telefoon"
               type="tel"
-              validation={ requiredValidation }
+              validation={ phoneValidation }
               formMethods={ formMethods }
             />
             <TextInputField
diff --git a/src/app/utils/getValueByPath.ts b/src/app/utils/getValueByPath.ts
new file mode 100644
index 0000000..4e4af8c
--- /dev/null
+++ b/src/app/utils/getValueByPath.ts
@@ -0,0 +1,40 @@
+/**
+ * Returns a value from an object by following a given path, which can be a string or array.
+ * 
+ * Example:
+ * 
+ * const obj = { user: { name: "Alice", age: 25, addresses: [{ city: "Wonderland" } } };
+ * const result = getValueByPath(obj, "user.address.city"); // Returns "Wonderland"
+ * 
+ * const obj = { users: [{ name: "Alice" }, { name: "Bob" }] };
+ * const result = getValueByPath(obj, "users[1].name"); // Returns "Bob"
+ * 
+ * COPY of Lodash GET function
+ */
+
+type Path = string | Array<string | number>
+type Value = boolean | string | object
+
+export function getValueByPath<T, R = undefined>(
+  obj: T,
+  path: Path,
+  defaultValue?: R
+): R | Value {
+  if (!obj || !path) return defaultValue as R
+
+  const pathArray = Array.isArray(path)
+    ? path
+    : path.replace(/\[(\d+)]/g, ".$1").split(".")
+
+  let current: Value = obj
+
+  for (const key of pathArray) {
+    if (current && typeof current === "object" && key in current) {
+      current = (current as Record<string | number, Value>)[key]
+    } else {
+      return defaultValue as R
+    }
+  }
+
+  return current
+}