diff --git a/C4/Members.pm b/C4/Members.pm
index 70158ec7ed..919f6c3890 100644
--- a/C4/Members.pm
+++ b/C4/Members.pm
@@ -48,9 +48,6 @@ BEGIN {
 
       IssueSlip
 
-      get_cardnumber_length
-      checkcardnumber
-
       DeleteUnverifiedOpacRegistrations
       DeleteExpiredOpacRegistrations
     );
@@ -287,65 +284,6 @@ sub GetAllIssues {
     return $sth->fetchall_arrayref( {} );
 }
 
-sub checkcardnumber {
-    my ( $cardnumber, $borrowernumber ) = @_;
-
-    # If cardnumber is null, we assume they're allowed.
-    return 0 unless defined $cardnumber;
-
-    my $dbh = C4::Context->dbh;
-    my $query = "SELECT * FROM borrowers WHERE cardnumber=?";
-    $query .= " AND borrowernumber <> ?" if ($borrowernumber);
-    my $sth = $dbh->prepare($query);
-    $sth->execute(
-        $cardnumber,
-        ( $borrowernumber ? $borrowernumber : () )
-    );
-
-    return 1 if $sth->fetchrow_hashref;
-
-    my ( $min_length, $max_length ) = get_cardnumber_length();
-    return 2
-        if length $cardnumber > $max_length
-        or length $cardnumber < $min_length;
-
-    return 0;
-}
-
-=head2 get_cardnumber_length
-
-    my ($min, $max) = C4::Members::get_cardnumber_length()
-
-Returns the minimum and maximum length for patron cardnumbers as
-determined by the CardnumberLength system preference, the
-BorrowerMandatoryField system preference, and the width of the
-database column.
-
-=cut
-
-sub get_cardnumber_length {
-    my $borrower = Koha::Database->new->schema->resultset('Borrower');
-    my $field_size = $borrower->result_source->column_info('cardnumber')->{size};
-    my ( $min, $max ) = ( 0, $field_size ); # borrowers.cardnumber is a nullable varchar(20)
-    $min = 1 if C4::Context->preference('BorrowerMandatoryField') =~ /cardnumber/;
-    if ( my $cardnumber_length = C4::Context->preference('CardnumberLength') ) {
-        # Is integer and length match
-        if ( $cardnumber_length =~ m|^\d+$| ) {
-            $min = $max = $cardnumber_length
-                if $cardnumber_length >= $min
-                    and $cardnumber_length <= $max;
-        }
-        # Else assuming it is a range
-        elsif ( $cardnumber_length =~ m|(\d*),(\d*)| ) {
-            $min = $1 if $1 and $min < $1;
-            $max = $2 if $2 and $max > $2;
-        }
-
-    }
-    $min = $max if $min > $max;
-    return ( $min, $max );
-}
-
 =head2 GetBorrowersToExpunge
 
   $borrowers = &GetBorrowersToExpunge(
diff --git a/Koha/Patrons/Import.pm b/Koha/Patrons/Import.pm
index 73d5355149..2e11a2ebb7 100644
--- a/Koha/Patrons/Import.pm
+++ b/Koha/Patrons/Import.pm
@@ -23,13 +23,13 @@ use Text::CSV;
 use Encode qw( decode_utf8 );
 use Try::Tiny qw( catch try );
 
-use C4::Members qw( checkcardnumber );
 use C4::Letters qw( GetPreparedLetter EnqueueLetter );
 
 use Koha::Libraries;
 use Koha::Patrons;
 use Koha::Patron::Categories;
 use Koha::Patron::Debarments qw( AddDebarment );
+use Koha::Policy::Patrons::Cardnumber;
 use Koha::DateUtils qw( dt_from_string output_pref );
 
 =head1 NAME
@@ -212,7 +212,8 @@ sub import_patrons {
             $is_new = 1;
         }
 
-        if ( C4::Members::checkcardnumber( $borrower{cardnumber}, $borrowernumber ) ) {
+        my $is_valid = Koha::Policy::Patrons::Cardnumber->is_valid($borrower{cardnumber}, $patron);
+        unless ( $is_valid ) {
             push @errors,
               {
                 invalid_cardnumber => 1,
diff --git a/Koha/Policy/Patrons/Cardnumber.pm b/Koha/Policy/Patrons/Cardnumber.pm
new file mode 100644
index 0000000000..43eb124050
--- /dev/null
+++ b/Koha/Policy/Patrons/Cardnumber.pm
@@ -0,0 +1,110 @@
+package Koha::Policy::Patrons::Cardnumber;
+
+# Copyright 2023 Koha Development team
+#
+# This file is part of Koha.
+#
+# Koha is free software; you can redistribute it and/or modify it
+# under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 3 of the License, or
+# (at your option) any later version.
+#
+# Koha is distributed in the hope that it will be useful, but
+# WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with Koha; if not, see <http://www.gnu.org/licenses>.
+
+use Modern::Perl;
+
+use C4::Context;
+
+use Koha::Patrons;
+use Koha::Result::Boolean;
+
+=head1 NAME
+
+Koha::Policy::Patrons::Cardnumber - module to deal with cardnumbers policy
+
+=head1 API
+
+=head2 Class Methods
+
+=head3 new
+
+=cut
+
+sub new {
+    return bless {}, shift;
+}
+
+=head3 is_valid
+
+    my $is_valid = Koha::Policy::Patrons::Cardnumber->is_valid( $cardnumber, [$patron] );
+
+Returns whether a cardnumber is valid of not for a given I<Koha::Patron> object.
+
+=cut
+
+sub is_valid {
+    my ( $class, $cardnumber, $patron ) = @_;
+
+    return Koha::Result::Boolean->new(0)->add_message( { message => "is_empty" } )
+        unless defined $cardnumber;
+
+    return Koha::Result::Boolean->new(0)->add_message( { message => "already_exists" } )
+        if Koha::Patrons->search(
+        {
+            cardnumber => $cardnumber,
+            ( $patron ? ( borrowernumber => { '!=' => $patron->borrowernumber } ) : () )
+        }
+    )->count;
+
+    my ( $min_length, $max_length ) = $class->get_valid_length();
+    return Koha::Result::Boolean->new(0)->add_message( { message => "invalid_length" } )
+        if length $cardnumber > $max_length
+        or length $cardnumber < $min_length;
+
+    return Koha::Result::Boolean->new(1);
+}
+
+=head2 get_valid_length
+
+    my ($min, $max) = Koha::Policy::Patrons::Cardnumber::get_valid_length();
+
+Returns the minimum and maximum length for patron cardnumbers as
+determined by the CardnumberLength system preference, the
+BorrowerMandatoryField system preference, and the width of the
+database column.
+
+=cut
+
+sub get_valid_length {
+    my ($class)    = @_;
+    my $borrower   = Koha::Database->new->schema->resultset('Borrower');
+    my $field_size = $borrower->result_source->column_info('cardnumber')->{size};
+    my ( $min, $max ) = ( 0, $field_size );    # borrowers.cardnumber is a nullable varchar(20)
+    $min = 1 if C4::Context->preference('BorrowerMandatoryField') =~ /cardnumber/;
+    if ( my $cardnumber_length = C4::Context->preference('CardnumberLength') ) {
+
+        # Is integer and length match
+        if ( $cardnumber_length =~ m|^\d+$| ) {
+            $min = $max = $cardnumber_length
+                if $cardnumber_length >= $min
+                and $cardnumber_length <= $max;
+        }
+
+        # Else assuming it is a range
+        elsif ( $cardnumber_length =~ m|(\d*),(\d*)| ) {
+            $min = $1 if $1 and $min < $1;
+            $max = $2 if $2 and $max > $2;
+        }
+
+    }
+    $min = $max if $min > $max;
+    return ( $min, $max );
+}
+
+1;
diff --git a/installer/onboarding.pl b/installer/onboarding.pl
index 68a1345df1..457f1fe278 100755
--- a/installer/onboarding.pl
+++ b/installer/onboarding.pl
@@ -22,12 +22,12 @@ use C4::Context;
 use C4::InstallAuth qw( checkauth get_template_and_user );
 use CGI qw ( -utf8 );
 use C4::Output qw( output_html_with_http_headers );
-use C4::Members qw( checkcardnumber );
 use Koha::Patrons;
 use Koha::Libraries;
 use Koha::Database;
 use Koha::Patrons;
 use Koha::Patron::Categories;
+use Koha::Policy::Patrons::Cardnumber;
 use Koha::ItemTypes;
 use Koha::CirculationRules;
 
@@ -141,12 +141,16 @@ if ( $step == 3 ) {
             $patron_category );
 
 
-        if ( my $error_code = checkcardnumber($cardnumber) ) {
-            if ( $error_code == 1 ) {
-                push @messages, { code => 'ERROR_cardnumber_already_exists' };
-            }
-            elsif ( $error_code == 2 ) {
-                push @messages, { code => 'ERROR_cardnumber_length' };
+        my $is_cardnumber_valid = Koha::Policy::Patrons::Cardnumber->is_valid($cardnumber);
+        unless ( $is_cardnumber_valid ) {
+            for my $m ( @{ $is_cardnumber_valid->messages } ) {
+                my $message = $m->message;
+                if ( $message eq 'already_exists' ) {
+                    push @messages, { code => 'ERROR_cardnumber_already_exists' };
+                }
+                elsif ( $message eq 'invalid_length' ) {
+                    push @messages, { code => 'ERROR_cardnumber_length' };
+                }
             }
         }
         elsif ( $firstpassword ne $secondpassword ) {
diff --git a/members/memberentry.pl b/members/memberentry.pl
index 70841759d7..89e32ff181 100755
--- a/members/memberentry.pl
+++ b/members/memberentry.pl
@@ -29,7 +29,6 @@ use CGI qw ( -utf8 );
 use C4::Auth qw( get_template_and_user haspermission );
 use C4::Context;
 use C4::Output qw( output_and_exit output_and_exit_if_error output_html_with_http_headers );
-use C4::Members qw( checkcardnumber get_cardnumber_length );
 use C4::Koha qw( GetAuthorisedValues );
 use C4::Letters qw( GetPreparedLetter EnqueueLetter SendQueuedMessages );
 use C4::Form::MessagingPreferences;
@@ -46,6 +45,7 @@ use Koha::Patron::Attribute::Types;
 use Koha::Patron::Categories;
 use Koha::Patron::HouseboundRole;
 use Koha::Patron::HouseboundRoles;
+use Koha::Policy::Patrons::Cardnumber;
 use Koha::Plugins;
 use Koha::Token;
 use Koha::SMS::Providers;
@@ -293,12 +293,16 @@ if ($op eq 'save' || $op eq 'insert'){
 
     $newdata{'cardnumber'} = $new_barcode;
 
-    if (my $error_code = checkcardnumber( $newdata{cardnumber}, $borrowernumber )){
-        push @errors, $error_code == 1
-            ? 'ERROR_cardnumber_already_exists'
-            : $error_code == 2
-                ? 'ERROR_cardnumber_length'
-                : ()
+    my $is_valid = Koha::Policy::Patrons::Cardnumber->is_valid($newdata{cardnumber}, $patron );
+    unless ($is_valid) {
+        for my $m ( @{ $is_valid->messages } ) {
+            my $message = $m->message;
+            if ( $message eq 'already_exists' ) {
+                $template->param( ERROR_cardnumber_already_exists => 1 );
+            } elsif ( $message eq 'invalid_length' ) {
+                $template->param( ERROR_cardnumber_length => 1 );
+            }
+        }
     }
 
     my $dateofbirth;
@@ -786,7 +790,7 @@ if(defined($data{'contacttitle'})){
 }
 
 
-my ( $min, $max ) = C4::Members::get_cardnumber_length();
+my ( $min, $max ) = Koha::Policy::Patrons::Cardnumber->get_valid_length();
 if ( defined $min ) {
     $template->param(
         minlength_cardnumber => $min,
diff --git a/opac/opac-memberentry.pl b/opac/opac-memberentry.pl
index ab99cb4e8c..f5a32db85a 100755
--- a/opac/opac-memberentry.pl
+++ b/opac/opac-memberentry.pl
@@ -28,7 +28,6 @@ use C4::Auth qw( get_template_and_user );
 use C4::Output qw( output_html_with_http_headers );
 use C4::Context;
 use C4::Letters qw( GetPreparedLetter EnqueueLetter SendQueuedMessages );
-use C4::Members qw( checkcardnumber );
 use C4::Form::MessagingPreferences;
 use Koha::AuthUtils;
 use Koha::Patrons;
@@ -43,6 +42,7 @@ use Koha::Patron::Attribute::Types;
 use Koha::Patron::Attributes;
 use Koha::Patron::Images;
 use Koha::Patron::Categories;
+use Koha::Policy::Patrons::Cardnumber;
 use Koha::Token;
 use Koha::AuthorisedValues;
 my $cgi = CGI->new;
@@ -88,7 +88,7 @@ if ( $action eq 'create' || $action eq 'new' ) {
 }
 my $libraries = Koha::Libraries->search($params);
 
-my ( $min, $max ) = C4::Members::get_cardnumber_length();
+my ( $min, $max ) = Koha::Policy::Patrons::Cardnumber->get_valid_length();
 if ( defined $min ) {
      $template->param(
          minlength_cardnumber => $min,
@@ -133,19 +133,25 @@ if ( $action eq 'create' ) {
     my @empty_mandatory_fields = (CheckMandatoryFields( \%borrower, $action ), CheckMandatoryAttributes( \%borrower, $attributes ) );
     my $invalidformfields = CheckForInvalidFields(\%borrower);
     delete $borrower{'password2'};
-    my $cardnumber_error_code;
+    my $is_cardnumber_valid;
     if ( !grep { $_ eq 'cardnumber' } @empty_mandatory_fields ) {
         # No point in checking the cardnumber if it's missing and mandatory, it'll just generate a
         # spurious length warning.
-        $cardnumber_error_code = checkcardnumber( $borrower{cardnumber}, $borrower{borrowernumber} );
+        my $patron = Koha::Patrons->find($borrower{borrowernumber});
+        $is_cardnumber_valid = Koha::Policy::Patrons::Cardnumber->is_valid($borrower{cardnumber}, $patron);
+        unless ($is_cardnumber_valid) {
+            for my $m ( @{ $is_cardnumber_valid->messages } ) {
+                my $message = $m->message;
+                if ( $message eq 'already_exists' ) {
+                    $template->param( cardnumber_already_exists => 1 );
+                } elsif ( $message eq 'invalid_length' ) {
+                    $template->param( cardnumber_wrong_length => 1 );
+                }
+            }
+        }
     }
 
-    if ( @empty_mandatory_fields || @$invalidformfields || $cardnumber_error_code || $conflicting_attribute ) {
-        if ( $cardnumber_error_code == 1 ) {
-            $template->param( cardnumber_already_exists => 1 );
-        } elsif ( $cardnumber_error_code == 2 ) {
-            $template->param( cardnumber_wrong_length => 1 );
-        }
+    if ( @empty_mandatory_fields || @$invalidformfields || !$is_cardnumber_valid || $conflicting_attribute ) {
 
         $template->param(
             empty_mandatory_fields => \@empty_mandatory_fields,
diff --git a/t/Members/cardnumber.t b/t/Members/cardnumber.t
deleted file mode 100755
index 7fddc7e676..0000000000
--- a/t/Members/cardnumber.t
+++ /dev/null
@@ -1,96 +0,0 @@
-#!/usr/bin/env perl
-
-use Modern::Perl;
-use Module::Load::Conditional qw/check_install/;
-use Test::More;
-use Test::MockModule;
-
-use t::lib::Mocks;
-
-use_ok('C4::Members', qw( get_cardnumber_length checkcardnumber ));
-
-BEGIN {
-    if ( check_install( module => 'Test::DBIx::Class' ) ) {
-        plan tests => 25;
-    } else {
-        plan skip_all => "Need Test::DBIx::Class"
-    }
-}
-
-use Test::DBIx::Class;
-
-my $db = Test::MockModule->new('Koha::Database');
-$db->mock( _new_schema => sub { return Schema(); } );
-
-my $dbh = C4::Context->dbh;
-my $rs = [];
-
-my $borrower = Koha::Schema->resultset('Borrower');
-my $cardnumber_size = $borrower->result_source->column_info('cardnumber')->{size};
-
-t::lib::Mocks::mock_preference('BorrowerMandatoryField', '');
-my $pref = "10";
-t::lib::Mocks::mock_preference('CardnumberLength', $pref);
-is_deeply( [ C4::Members::get_cardnumber_length() ], [ 10, 10 ], '10 => min=10 and max=10');
-$dbh->{mock_add_resultset} = $rs;
-is( C4::Members::checkcardnumber( q{123456789} ), 2, "123456789 is shorter than $pref");
-$dbh->{mock_add_resultset} = $rs;
-is( C4::Members::checkcardnumber( q{1234567890123456} ), 2, "1234567890123456 is longer than $pref");
-$dbh->{mock_add_resultset} = $rs;
-is( C4::Members::checkcardnumber( q{1234567890} ), 0, "1234567890 is equal to $pref");
-
-$pref = q|10,10|; # Same as before !
-t::lib::Mocks::mock_preference('CardnumberLength', $pref);
-is_deeply( [ C4::Members::get_cardnumber_length() ], [ 10, 10 ], '10,10 => min=10 and max=10');
-$dbh->{mock_add_resultset} = $rs;
-is( C4::Members::checkcardnumber( q{123456789} ), 2, "123456789 is shorter than $pref");
-$dbh->{mock_add_resultset} = $rs;
-is( C4::Members::checkcardnumber( q{1234567890123456} ), 2, "1234567890123456 is longer than $pref");
-$dbh->{mock_add_resultset} = $rs;
-is( C4::Members::checkcardnumber( q{1234567890} ), 0, "1234567890 is equal to $pref");
-
-$pref = q|8,10|; # between 8 and 10 chars
-t::lib::Mocks::mock_preference('CardnumberLength', $pref);
-is_deeply( [ C4::Members::get_cardnumber_length() ], [ 8, 10 ], '8,10 => min=8 and max=10');
-$dbh->{mock_add_resultset} = $rs;
-is( C4::Members::checkcardnumber( q{12345678} ), 0, "12345678 matches $pref");
-$dbh->{mock_add_resultset} = $rs;
-is( C4::Members::checkcardnumber( q{1234567890123456} ), 2, "1234567890123456 is longer than $pref");
-$dbh->{mock_add_resultset} = $rs;
-is( C4::Members::checkcardnumber( q{1234567} ), 2, "1234567 is shorter than $pref");
-$dbh->{mock_add_resultset} = $rs;
-is( C4::Members::checkcardnumber( q{1234567890} ), 0, "1234567890 matches $pref");
-
-$pref = q|8,|; # At least 8 chars
-t::lib::Mocks::mock_preference('CardnumberLength', $pref);
-is_deeply( [ C4::Members::get_cardnumber_length() ], [ 8, $cardnumber_size ], "8, => min=8 and max=$cardnumber_size");
-$dbh->{mock_add_resultset} = $rs;
-is( C4::Members::checkcardnumber( q{1234567} ), 2, "1234567 is shorter than $pref");
-$dbh->{mock_add_resultset} = $rs;
-is( C4::Members::checkcardnumber( q{1234567890123456} ), 0, "1234567890123456 matches $pref");
-$dbh->{mock_add_resultset} = $rs;
-is( C4::Members::checkcardnumber( q{1234567890} ), 0, "1234567890 matches $pref");
-
-$pref = q|,8|; # max 8 chars
-t::lib::Mocks::mock_preference('CardnumberLength', $pref);
-is_deeply( [ C4::Members::get_cardnumber_length() ], [ 0, 8 ], ',8 => min=0 and max=8');
-$dbh->{mock_add_resultset} = $rs;
-is( C4::Members::checkcardnumber( q{1234567} ), 0, "1234567 matches $pref");
-$dbh->{mock_add_resultset} = $rs;
-is( C4::Members::checkcardnumber( q{1234567890123456} ), 2, "1234567890123456 is longer than $pref");
-$dbh->{mock_add_resultset} = $rs;
-is( C4::Members::checkcardnumber( q{1234567890} ), 2, "1234567890 is longer than $pref");
-
-$pref = sprintf(',%d', $cardnumber_size+1);
-t::lib::Mocks::mock_preference('CardnumberLength', $pref);
-is_deeply( [ C4::Members::get_cardnumber_length() ], [ 0, $cardnumber_size ],
-    sprintf(",%d => min=0 and max=%d",$cardnumber_size+1,$cardnumber_size) );
-$dbh->{mock_add_resultset} = $rs;
-
-my $generated_cardnumber = sprintf("%s1234567890",q|9|x$cardnumber_size);
-is( C4::Members::checkcardnumber( $generated_cardnumber ), 2, "$generated_cardnumber is longer than $pref => $cardnumber_size is max!");
-
-$pref = q|,8|; # max 8 chars
-t::lib::Mocks::mock_preference('CardnumberLength', $pref);
-t::lib::Mocks::mock_preference('BorrowerMandatoryField', 'cardnumber');
-is_deeply( [ C4::Members::get_cardnumber_length() ], [ 1, 8 ], ',8 => min=1 and max=8 if cardnumber is mandatory');
diff --git a/t/db_dependent/Koha/Policy/Patrons/Cardnumber.t b/t/db_dependent/Koha/Policy/Patrons/Cardnumber.t
new file mode 100755
index 0000000000..986963c735
--- /dev/null
+++ b/t/db_dependent/Koha/Policy/Patrons/Cardnumber.t
@@ -0,0 +1,163 @@
+#!/usr/bin/perl
+
+# Copyright 2023 Koha Development team
+#
+# This file is part of Koha
+#
+# Koha is free software; you can redistribute it and/or modify it
+# under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 3 of the License, or
+# (at your option) any later version.
+#
+# Koha is distributed in the hope that it will be useful, but
+# WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with Koha; if not, see <http://www.gnu.org/licenses>.
+
+use Modern::Perl;
+
+use Test::More tests => 3;
+
+use Koha::Database;
+use Koha::Policy::Patrons::Cardnumber;
+use t::lib::Mocks;
+use t::lib::TestBuilder;
+
+my $schema  = Koha::Database->new->schema;
+my $builder = t::lib::TestBuilder->new;
+
+subtest 'is_valid' => sub {
+
+    plan tests => 21;
+
+    $schema->storage->txn_begin;
+
+    my $patron = $builder->build_object( { class => 'Koha::Patrons' } );
+
+    t::lib::Mocks::mock_preference( 'CardnumberLength', '' );
+
+    my $policy = Koha::Policy::Patrons::Cardnumber->new;
+
+    my $is_valid = $policy->is_valid( $patron->cardnumber );
+    ok( !$is_valid, "Cardnumber in use, cannot be reused" );
+
+    $is_valid = $policy->is_valid( $patron->cardnumber, $patron );
+    ok( $is_valid, "Cardnumber in use but can be used by the same patron" );
+
+    my $tmp_patron           = $builder->build_object( { class => 'Koha::Patrons' } );
+    my $available_cardnumber = $tmp_patron->cardnumber;
+    $tmp_patron->delete;
+    $is_valid = $policy->is_valid($available_cardnumber);
+    ok( $is_valid, "Cardnumber not in use" );
+
+    t::lib::Mocks::mock_preference( 'CardnumberLength', '4' );
+
+    $is_valid = $policy->is_valid("12345");
+    ok( !$is_valid, "Invalid cardnumber length" );
+
+    $is_valid = $policy->is_valid("123");
+    ok( !$is_valid, "Invalid cardnumber length" );
+
+    my $pref = "10";
+    t::lib::Mocks::mock_preference( 'CardnumberLength', $pref );
+    ok( !$policy->is_valid(q{123456789}),        "123456789 is shorter than $pref" );
+    ok( !$policy->is_valid(q{1234567890123456}), "1234567890123456 is longer than $pref" );
+    ok( $policy->is_valid(q{1234567890}),        "1234567890 is equal to $pref" );
+
+    $pref = q|10,10|;    # Same as before !
+    t::lib::Mocks::mock_preference( 'CardnumberLength', $pref );
+    ok( !$policy->is_valid(q{123456789}),        "123456789 is shorter than $pref" );
+    ok( !$policy->is_valid(q{1234567890123456}), "1234567890123456 is longer than $pref" );
+    ok( $policy->is_valid(q{1234567890}),        "1234567890 is equal to $pref" );
+
+    $pref = q|8,10|;     # between 8 and 10 chars
+    t::lib::Mocks::mock_preference( 'CardnumberLength', $pref );
+    ok( $policy->is_valid(q{12345678}),          "12345678 matches $pref" );
+    ok( !$policy->is_valid(q{1234567890123456}), "1234567890123456 is longer than $pref" );
+    ok( !$policy->is_valid(q{1234567}),          "1234567 is shorter than $pref" );
+    ok( $policy->is_valid(q{1234567890}),        "1234567890 matches $pref" );
+
+    $pref = q|8,|;       # At least 8 chars
+    t::lib::Mocks::mock_preference( 'CardnumberLength', $pref );
+    ok( !$policy->is_valid(q{1234567}),         "1234567 is shorter than $pref" );
+    ok( $policy->is_valid(q{1234567890123456}), "1234567890123456 matches $pref" );
+    ok( $policy->is_valid(q{1234567890}),       "1234567890 matches $pref" );
+
+    $pref = q|,8|;       # max 8 chars
+    t::lib::Mocks::mock_preference( 'CardnumberLength', $pref );
+    ok( $policy->is_valid(q{1234567}),           "1234567 matches $pref" );
+    ok( !$policy->is_valid(q{1234567890123456}), "1234567890123456 is longer than $pref" );
+    ok( !$policy->is_valid(q{1234567890}),       "1234567890 is longer than $pref" );
+
+    $schema->storage->txn_rollback;
+};
+
+subtest 'get_valid_length' => sub {
+
+    plan tests => 5;
+
+    $schema->storage->txn_begin;
+
+    my $policy = Koha::Policy::Patrons::Cardnumber->new;
+
+    t::lib::Mocks::mock_preference( 'BorrowerMandatoryField', '' );
+
+    my $pref = "10";
+    t::lib::Mocks::mock_preference( 'CardnumberLength', $pref );
+    is_deeply( [ $policy->get_valid_length() ], [ 10, 10 ], '10 => min=10 and max=10' );
+
+    $pref = q|10,10|;    # Same as before !
+    t::lib::Mocks::mock_preference( 'CardnumberLength', $pref );
+    is_deeply( [ $policy->get_valid_length() ], [ 10, 10 ], '10,10 => min=10 and max=10' );
+
+    $pref = q|8,10|;     # between 8 and 10 chars
+    t::lib::Mocks::mock_preference( 'CardnumberLength', $pref );
+    is_deeply( [ $policy->get_valid_length() ], [ 8, 10 ], '8,10 => min=8 and max=10' );
+
+    $pref = q|,8|;       # max 8 chars
+    t::lib::Mocks::mock_preference( 'CardnumberLength', $pref );
+    is_deeply( [ $policy->get_valid_length() ], [ 0, 8 ], ',8 => min=0 and max=8' );
+
+    $pref = q|,8|;       # max 8 chars
+    t::lib::Mocks::mock_preference( 'CardnumberLength',       $pref );
+    t::lib::Mocks::mock_preference( 'BorrowerMandatoryField', 'cardnumber' );
+    is_deeply( [ $policy->get_valid_length() ], [ 1, 8 ], ',8 => min=1 and max=8 if cardnumber is mandatory' );
+
+    $schema->storage->txn_rollback;
+
+};
+
+subtest 'compare with DB data size' => sub {
+
+    plan tests => 3;
+
+    $schema->storage->txn_begin;
+
+    my $policy          = Koha::Policy::Patrons::Cardnumber->new;
+    my $borrower        = Koha::Schema->resultset('Borrower');
+    my $cardnumber_size = $borrower->result_source->column_info('cardnumber')->{size};
+    t::lib::Mocks::mock_preference( 'BorrowerMandatoryField', '' );
+
+    my $pref = q|8,|;    # At least 8 chars
+    t::lib::Mocks::mock_preference( 'CardnumberLength', $pref );
+    is_deeply( [ $policy->get_valid_length() ], [ 8, $cardnumber_size ], "8, => min=8 and max=$cardnumber_size" );
+
+    $pref = sprintf( ',%d', $cardnumber_size + 1 );
+    t::lib::Mocks::mock_preference( 'CardnumberLength', $pref );
+    is_deeply(
+        [ $policy->get_valid_length() ], [ 0, $cardnumber_size ],
+        sprintf( ",%d => min=0 and max=%d", $cardnumber_size + 1, $cardnumber_size )
+    );
+
+    my $generated_cardnumber = sprintf( "%s1234567890", q|9| x $cardnumber_size );
+    ok(
+        !$policy->is_valid($generated_cardnumber),
+        "$generated_cardnumber is longer than $pref => $cardnumber_size is max!"
+    );
+
+    $schema->storage->txn_rollback;
+
+};
diff --git a/t/db_dependent/Members.t b/t/db_dependent/Members.t
index 7d9852af57..7dceafd1bb 100755
--- a/t/db_dependent/Members.t
+++ b/t/db_dependent/Members.t
@@ -17,7 +17,7 @@
 
 use Modern::Perl;
 
-use Test::More tests => 53;
+use Test::More tests => 50;
 use Test::MockModule;
 use Test::Exception;
 
@@ -33,7 +33,7 @@ use t::lib::Mocks;
 use t::lib::TestBuilder;
 
 BEGIN {
-        use_ok('C4::Members', qw( checkcardnumber GetBorrowersToExpunge DeleteUnverifiedOpacRegistrations DeleteExpiredOpacRegistrations ));
+        use_ok('C4::Members', qw( GetBorrowersToExpunge DeleteUnverifiedOpacRegistrations DeleteExpiredOpacRegistrations ));
 }
 
 my $schema = Koha::Database->schema;
@@ -58,9 +58,6 @@ my $EMAIL             = "Marie\@email.com";
 my $EMAILPRO          = "Marie\@work.com";
 my $PHONE             = "555-12123";
 
-# XXX should be randomised and checked against the database
-my $IMPOSSIBLE_CARDNUMBER = "XYZZZ999";
-
 t::lib::Mocks::mock_userenv();
 
 # Make a borrower for testing
@@ -104,22 +101,6 @@ ok ( $changedmember->{firstname} eq $CHANGED_FIRSTNAME &&
      , "Member Changed")
   or diag("Mismatching member details: ".Dumper($member, $changedmember));
 
-t::lib::Mocks::mock_preference( 'CardnumberLength', '' );
-C4::Context->clear_syspref_cache();
-
-my $checkcardnum=C4::Members::checkcardnumber($CARDNUMBER, "");
-is ($checkcardnum, "1", "Card No. in use");
-
-$checkcardnum=C4::Members::checkcardnumber($IMPOSSIBLE_CARDNUMBER, "");
-is ($checkcardnum, "0", "Card No. not used");
-
-t::lib::Mocks::mock_preference( 'CardnumberLength', '4' );
-C4::Context->clear_syspref_cache();
-
-$checkcardnum=C4::Members::checkcardnumber($IMPOSSIBLE_CARDNUMBER, "");
-is ($checkcardnum, "2", "Card number is too long");
-
-
 # Add a new borrower
 %data = (
     cardnumber   => "123456789",