diff --git a/src/vcard.nim b/src/vcard.nim
index 95ee403..08c6a7e 100644
--- a/src/vcard.nim
+++ b/src/vcard.nim
@@ -55,6 +55,14 @@ proc readVCard*(p: var VCardParser): VCard =
   if result.parsedVersion == VCardV3:
     while (p.skip(CRLF, true)): discard
 
+  try:
+    if result.parsedVersion == VCardV3:
+      cast[VCard3](result).validate()
+    else:
+      cast[VCard4](result).validate()
+  except ValueError as exc:
+    p.error(exc.msg)
+
 proc initVCardParser*(input: Stream, filename = "input"): VCardParser =
   result.filename = filename
   lexer.open(result, input)
diff --git a/src/vcard/vcard3.nim b/src/vcard/vcard3.nim
index f2a1198..b318834 100644
--- a/src/vcard/vcard3.nim
+++ b/src/vcard/vcard3.nim
@@ -707,18 +707,39 @@ genPropertyAccessors(propertyCardMap.pairs.toSeq -->
   filter(not [pnVersion].contains(it[0])))
 
 func version*(vc3: VCard3): VC3_Version =
-  ## Return the VERSION property.
-  let found = findFirst[VC3_Version, VC3_Property](vc3.content)
-  if found.isSome: return found.get
-  else: return VC3_Version(
-    propertyId: vc3.content.len + 1,
-    group: none[string](),
-    name: "VERSION",
-    value: "3.0")
+  ## Return the canonical VERSION property for a vCard 3.0 card.
+  result = newVC3_Version()
 
 func xTypes*(vc3: VCard3): seq[VC3_XType] = findAll[VC3_XType, VC3_Property](vc3.content)
   ## Return all extended properties (starting with `x-`).
 
+func validate*(vc3: VCard3): void =
+  ## Validate property cardinality for a vCard 3.0 card.
+  for pn in VC3_PropertyName:
+    if pn == pnVersion:
+      continue
+
+    let count = vc3.content.countIt(it.name == $pn)
+
+    case propertyCardMap[pn]
+    of vpcExactlyOne:
+      if count != 1:
+        raise newException(ValueError,
+          "VCard should have exactly one $# property, but $# were found" %
+            [$pn, $count])
+    of vpcAtLeastOne:
+      if count < 1:
+        raise newException(ValueError,
+          "VCard should have at least one $# property, but $# were found" %
+            [$pn, $count])
+    of vpcAtMostOne:
+      if count > 1:
+        raise newException(ValueError,
+          "VCard should have at most one $# property, but $# were found" %
+            [$pn, $count])
+    of vpcAny:
+      discard
+
 # Setters
 # =============================================================================
 
@@ -1030,6 +1051,7 @@ proc readBinaryValue(
 
 proc parseContentLines*(p: var VCardParser): seq[VC3_Property] =
   result = @[]
+  var sawVersion = false
 
   macro assignCommon(assign: untyped): untyped =
     result = assign
@@ -1271,9 +1293,11 @@ proc parseContentLines*(p: var VCardParser): seq[VC3_Property] =
       result.add(newVC3_URL(group = group, value = p.readValue))
 
     of $pnVersion:
+      if sawVersion:
+        p.error("VCard should have exactly one VERSION property, but 2 were found")
       p.expect("3.0")
       p.validateNoParameters(params, "VERSION")
-      result.add(newVC3_Version(group = group))
+      sawVersion = true
 
     of $pnClass:
       result.add(newVC3_Class(group = group, value = p.readValue))
@@ -1312,6 +1336,9 @@ proc parseContentLines*(p: var VCardParser): seq[VC3_Property] =
 
     p.expect("\r\n")
 
+  if not sawVersion:
+    p.error("VCard should have exactly one VERSION property, but 0 were found")
+
 #[
 Simplified Parsing Diagram
 
diff --git a/src/vcard/vcard4.nim b/src/vcard/vcard4.nim
index cb3046c..bf75eb2 100644
--- a/src/vcard/vcard4.nim
+++ b/src/vcard/vcard4.nim
@@ -968,6 +968,56 @@ genPidAccessors(supportedParams["PID"].toSeq())
 genPrefAccessors(supportedParams["PREF"].toSeq())
 genTypeAccessors(supportedParams["TYPE"].toSeq())
 
+func countCardinalityInstances(vc4: VCard4, propName: string): int =
+  var altIds = initHashSet[string]()
+
+  for p in vc4.content:
+    if p.name != propName:
+      continue
+
+    if p.altId.isSome:
+      altIds.incl(p.altId.get)
+    else:
+      inc result
+
+  result += altIds.len
+
+func validate*(vc4: VCard4): void =
+  ## Validate property cardinality for a vCard 4.0 card.
+  for pn in VC4_PropertyName:
+    if pn == pnVersion:
+      continue
+
+    if not propertyCardMap.contains(pn):
+      continue
+
+    let rawCount = vc4.content.countIt(it.name == $pn)
+    let cardinalityCount =
+      case propertyCardMap[pn]
+      of vpcExactlyOne, vpcAtMostOne:
+        vc4.countCardinalityInstances($pn)
+      of vpcAtLeastOne, vpcAny:
+        rawCount
+
+    case propertyCardMap[pn]
+    of vpcExactlyOne:
+      if cardinalityCount != 1:
+        raise newException(ValueError,
+          "VCard should have exactly one $# property, but $# were found" %
+            [$pn, $cardinalityCount])
+    of vpcAtLeastOne:
+      if cardinalityCount < 1:
+        raise newException(ValueError,
+          "VCard should have at least one $# property, but $# were found" %
+            [$pn, $cardinalityCount])
+    of vpcAtMostOne:
+      if cardinalityCount > 1:
+        raise newException(ValueError,
+          ("VCard should have at most one $# property, but $# " &
+           "distinct properties were found") % [$pn, $cardinalityCount])
+    of vpcAny:
+      discard
+
 # Setters
 # =============================================================================
 
@@ -1382,6 +1432,7 @@ macro genPropParsers(
 
 proc parseContentLines*(p: var VCardParser): seq[VC4_Property] =
   result = @[]
+  var sawVersion = false
 
   while true:
     let group = p.readGroup
@@ -1392,10 +1443,20 @@ proc parseContentLines*(p: var VCardParser): seq[VC4_Property] =
     let params = p.readParams
     p.expect(":")
 
-    genPropParsers(fixedValueTypeProperties, group, name, params, result, p)
+    if name == $pnVersion:
+      if sawVersion:
+        p.error("VCard should have exactly one VERSION property, but 2 were found")
+      p.validateType(params, vtText)
+      p.expect("4.0")
+      sawVersion = true
+    else:
+      genPropParsers(fixedValueTypeProperties, group, name, params, result, p)
 
     p.expect(CRLF)
 
+  if not sawVersion:
+    p.error("VCard should have exactly one VERSION property, but 0 were found")
+
 
 # Private Function Unit Tests
 # ============================================================================
diff --git a/tests/tvcard3.nim b/tests/tvcard3.nim
index ca991ae..e212e56 100644
--- a/tests/tvcard3.nim
+++ b/tests/tvcard3.nim
@@ -1,4 +1,4 @@
-import std/[options, strutils, times, unittest]
+import std/[options, sequtils, strutils, times, unittest]
 import zero_functional
 
 import vcard
@@ -57,6 +57,7 @@ suite "vcard/vcard3":
       "BEGIN:vCard\r\n" &
       "VERSION:3.0\r\n" &
       "FN:Frank Dawson\r\n" &
+      "N:Dawson;Frank;;;\r\n" &
       "ORG:Lotus Development Corporation\r\n" &
       "ADR;TYPE=WORK,POSTAL,PARCEL:;;6544 Battleford Drive\r\n" &
       " ;Raleigh;NC;27613-3502;U.S.A.\r\n" &
@@ -71,6 +72,7 @@ suite "vcard/vcard3":
       "BEGIN:vCard\r\n" &
       "VERSION:3.0\r\n" &
       "FN:Tim Howes\r\n" &
+      "N:Howes;Tim;;;\r\n" &
       "ORG:Netscape Communications Corp.\r\n" &
       "ADR;TYPE=WORK:;;501 E. Middlefield Rd.;Mountain View;\r\n" &
       " CA; 94043;U.S.A.\r\n" &
@@ -104,6 +106,25 @@ suite "vcard/vcard3":
         "VERSION:3.0",
         "FN:John Smith"))
 
+  test "spec: parser rejects duplicate single-cardinality vCard 3 properties":
+    expect(VCardParsingError):
+      discard parseVCards(vcard3Doc(
+        "VERSION:3.0",
+        "FN:John Smith",
+        "N:Smith;John;;;",
+        "BDAY:2000-01-01",
+        "BDAY:2000-01-02"))
+
+  test "spec: VERSION is not stored as vCard 3 content":
+    let parsed = parseSingleVCard3(vcard3Doc(
+      "VERSION:3.0",
+      "FN:John Smith",
+      "N:Smith;John;;;"))
+
+    check:
+      parsed.version.value == "3.0"
+      parsed.content.countIt(it of VC3_Version) == 0
+
   test "spec: simple text values decode RFC 2426 escapes when parsing":
     let parsed = parseSingleVCard3(vcard3Doc(
       "VERSION:3.0",
diff --git a/tests/tvcard4.nim b/tests/tvcard4.nim
index a63ee41..e938b1c 100644
--- a/tests/tvcard4.nim
+++ b/tests/tvcard4.nim
@@ -1,4 +1,4 @@
-import std/[options, strutils, tables, unittest]
+import std/[options, sequtils, strutils, tables, unittest]
 import zero_functional
 
 import vcard
@@ -203,6 +203,7 @@ suite "vcard/vcard4":
       madeUpProp.value == "Sample value for my made-up prop."
 
   let cardWithAltBdayStr = testVCardTemplate % [(
+    "FN:Simon Perreault\r\n" &
     "BDAY;VALUE=text;ALTID=1:20th century\r\n" &
     "BDAY;VALUE=date-and-or-time;ALTID=1:19650321\r\n"
   )]
@@ -210,6 +211,14 @@ suite "vcard/vcard4":
   test "single-cardinality properties allow multiples with ALTID":
     check parseVCards(cardWithAltBdayStr).len == 1
 
+  test "single-cardinality properties reject multiples without ALTID":
+    expect(VCardParsingError):
+      discard parseVCards(testVCardTemplate % [(
+        "FN:Simon Perreault\r\n" &
+        "BDAY;VALUE=text:20th century\r\n" &
+        "BDAY;VALUE=date-and-or-time:19650321\r\n"
+      )])
+
   let hasAltBdays = cast[VCard4](parseVCards(cardWithAltBdayStr)[0])
 
   test "properties with cardinality 1 and altids return the first found by default":
@@ -222,6 +231,7 @@ suite "vcard/vcard4":
     check:
       hasAltBdays.content.len == 3
       hasAltBdays.bday.isSome
+      hasAltBdays.content.countIt(it of VC4_Version) == 0
 
     let allBdays = allAlternatives[VC4_Bday](hasAltBdays)
     check: