diff --git a/src/models/Address.ts b/src/models/Address.ts
index ccc2c70..735ecd3 100644
--- a/src/models/Address.ts
+++ b/src/models/Address.ts
@@ -76,12 +76,12 @@ export class Address {
   /**
    * Used to link the address to participants.
    */
-  @OneToMany(() => Participant, participant => participant.address)
+  @OneToMany(() => Participant, participant => participant.address, { nullable: true })
   participants: Participant[];
 
   /**
    * Used to link the address to runner groups.
    */
-  @OneToMany(() => RunnerOrganisation, group => group.address)
+  @OneToMany(() => RunnerOrganisation, group => group.address, { nullable: true })
   groups: RunnerOrganisation[];
 }
diff --git a/src/models/DistanceDonation.ts b/src/models/DistanceDonation.ts
index 878f8cb..79bf0b8 100644
--- a/src/models/DistanceDonation.ts
+++ b/src/models/DistanceDonation.ts
@@ -13,7 +13,7 @@ export class DistanceDonation extends Donation {
    * The runner associated.
    */
   @IsNotEmpty()
-  @ManyToOne(() => Runner, runner => runner.distanceDonations)
+  @ManyToOne(() => Runner, runner => runner.distanceDonations, { nullable: true })
   runner: Runner;
 
   /**
diff --git a/src/models/Donation.ts b/src/models/Donation.ts
index 7143c99..b94e182 100644
--- a/src/models/Donation.ts
+++ b/src/models/Donation.ts
@@ -24,7 +24,7 @@ export abstract class Donation {
    * The donations's donor.
    */
   @IsNotEmpty()
-  @ManyToOne(() => Participant, donor => donor.donations)
+  @ManyToOne(() => Participant, donor => donor.donations, { nullable: true })
   donor: Participant;
 
   /**
diff --git a/src/models/GroupContact.ts b/src/models/GroupContact.ts
index 745174f..5d12066 100644
--- a/src/models/GroupContact.ts
+++ b/src/models/GroupContact.ts
@@ -55,7 +55,7 @@ export class GroupContact {
    * Optional
    */
   @IsOptional()
-  @ManyToOne(() => Address, address => address.participants)
+  @ManyToOne(() => Address, address => address.participants, { nullable: true })
   address?: Address;
 
   /**
@@ -79,12 +79,12 @@ export class GroupContact {
   /**
    * Used to link the contact as the donor of a donation.
    */
-  @OneToMany(() => Donation, donation => donation.donor)
+  @OneToMany(() => Donation, donation => donation.donor, { nullable: true })
   donations: Donation[];
 
   /**
     * Used to link runners to donations.
     */
-  @OneToMany(() => RunnerGroup, group => group.contact)
+  @OneToMany(() => RunnerGroup, group => group.contact, { nullable: true })
   groups: RunnerGroup[];
 }
\ No newline at end of file
diff --git a/src/models/Participant.ts b/src/models/Participant.ts
index bcbf5ca..e80d348 100644
--- a/src/models/Participant.ts
+++ b/src/models/Participant.ts
@@ -53,7 +53,7 @@ export abstract class Participant {
    * The participant's address.
    * Optional
    */
-  @ManyToOne(() => Address, address => address.participants)
+  @ManyToOne(() => Address, address => address.participants, { nullable: true })
   address?: Address;
 
   /**
@@ -77,6 +77,6 @@ export abstract class Participant {
   /**
    * Used to link the participant as the donor of a donation.
    */
-  @OneToMany(() => Donation, donation => donation.donor)
+  @OneToMany(() => Donation, donation => donation.donor, { nullable: true })
   donations: Donation[];
 }
\ No newline at end of file
diff --git a/src/models/Permission.ts b/src/models/Permission.ts
index e9b049b..751efe3 100644
--- a/src/models/Permission.ts
+++ b/src/models/Permission.ts
@@ -23,13 +23,13 @@ export abstract class Permission {
   /**
    * users
    */
-  @OneToMany(() => User, user => user.permissions)
+  @OneToMany(() => User, user => user.permissions, { nullable: true })
   users: User[]
 
   /**
    * groups
    */
-  @OneToMany(() => UserGroup, group => group.permissions)
+  @OneToMany(() => UserGroup, group => group.permissions, { nullable: true })
   groups: UserGroup[]
 
   /**
diff --git a/src/models/Runner.ts b/src/models/Runner.ts
index 3a8532a..7423c22 100644
--- a/src/models/Runner.ts
+++ b/src/models/Runner.ts
@@ -15,25 +15,25 @@ export class Runner extends Participant {
    * The runner's associated group.
    */
   @IsNotEmpty()
-  @ManyToOne(() => RunnerGroup, group => group.runners)
+  @ManyToOne(() => RunnerGroup, group => group.runners, { nullable: true })
   group: RunnerGroup;
   
   /**
    * Used to link runners to donations.
    */
-  @OneToMany(() => DistanceDonation, distanceDonation => distanceDonation.runner)
+  @OneToMany(() => DistanceDonation, distanceDonation => distanceDonation.runner, { nullable: true })
   distanceDonations: DistanceDonation[];
 
   /**
    * Used to link runners to cards.
    */
-  @OneToMany(() => RunnerCard, card => card.runner)
+  @OneToMany(() => RunnerCard, card => card.runner, { nullable: true })
   cards: RunnerCard[];
 
   /**
    * Used to link runners to a scans
    */
-  @OneToMany(() => Scan, scan => scan.runner)
+  @OneToMany(() => Scan, scan => scan.runner, { nullable: true })
   scans: Scan[];
 
   @IsInt() 
diff --git a/src/models/RunnerCard.ts b/src/models/RunnerCard.ts
index f978d0c..8b0e05b 100644
--- a/src/models/RunnerCard.ts
+++ b/src/models/RunnerCard.ts
@@ -26,7 +26,7 @@ export class RunnerCard {
    * The runner that is currently associated with this card.
    */
   @IsOptional()
-  @ManyToOne(() => Runner, runner => runner.cards)
+  @ManyToOne(() => Runner, runner => runner.cards, { nullable: true })
   runner: Runner;
 
   /**
@@ -51,6 +51,6 @@ export class RunnerCard {
   /**
    * Used to link cards to a track scans.
    */
-  @OneToMany(() => TrackScan, scan => scan.track)
+  @OneToMany(() => TrackScan, scan => scan.track, { nullable: true })
   scans: TrackScan[];
 }
diff --git a/src/models/RunnerGroup.ts b/src/models/RunnerGroup.ts
index a7c199b..2cd3694 100644
--- a/src/models/RunnerGroup.ts
+++ b/src/models/RunnerGroup.ts
@@ -35,12 +35,12 @@ export abstract class RunnerGroup {
    * Optional
    */
   @IsOptional()
-  @ManyToOne(() => GroupContact, contact => contact.groups)
+  @ManyToOne(() => GroupContact, contact => contact.groups, { nullable: true })
   contact?: GroupContact;
 
   /**
    * Used to link runners to a runner group.
    */
-  @OneToMany(() => Runner, runner => runner.group)
+  @OneToMany(() => Runner, runner => runner.group, { nullable: true })
   runners: Runner[];
 }
\ No newline at end of file
diff --git a/src/models/RunnerOrganisation.ts b/src/models/RunnerOrganisation.ts
index 958b363..4245fa0 100644
--- a/src/models/RunnerOrganisation.ts
+++ b/src/models/RunnerOrganisation.ts
@@ -15,12 +15,12 @@ export class RunnerOrganisation extends RunnerGroup {
    * Optional
    */
   @IsOptional()
-  @ManyToOne(() => Address, address => address.groups)
+  @ManyToOne(() => Address, address => address.groups, { nullable: true })
   address?: Address;
 
     /**
    * Used to link teams to runner groups.
    */
-  @OneToMany(() => RunnerTeam, team => team.parentGroup)
+  @OneToMany(() => RunnerTeam, team => team.parentGroup, { nullable: true })
   teams: RunnerTeam[];
 }
\ No newline at end of file
diff --git a/src/models/RunnerTeam.ts b/src/models/RunnerTeam.ts
index f12c5eb..5adc60d 100644
--- a/src/models/RunnerTeam.ts
+++ b/src/models/RunnerTeam.ts
@@ -14,6 +14,6 @@ export class RunnerTeam extends RunnerGroup {
    * Optional
    */
   @IsNotEmpty()
-  @ManyToOne(() => RunnerOrganisation, org => org.teams)
+  @ManyToOne(() => RunnerOrganisation, org => org.teams, { nullable: true })
   parentGroup?: RunnerOrganisation;
 }
\ No newline at end of file
diff --git a/src/models/Scan.ts b/src/models/Scan.ts
index 055e94b..3fd64ed 100644
--- a/src/models/Scan.ts
+++ b/src/models/Scan.ts
@@ -25,7 +25,7 @@ export abstract class Scan {
    * The associated runner.
    */
   @IsNotEmpty()
-  @ManyToOne(() => Runner, runner => runner.scans)
+  @ManyToOne(() => Runner, runner => runner.scans, { nullable: true })
   runner: Runner;
 
   /**
diff --git a/src/models/ScanStation.ts b/src/models/ScanStation.ts
index fd30a34..c529b25 100644
--- a/src/models/ScanStation.ts
+++ b/src/models/ScanStation.ts
@@ -34,7 +34,7 @@ export class ScanStation {
    * The track this station is associated with.
    */
   @IsNotEmpty()
-  @ManyToOne(() => Track, track => track.stations)
+  @ManyToOne(() => Track, track => track.stations, { nullable: true })
   track: Track;
 
   /**
@@ -56,6 +56,6 @@ export class ScanStation {
   /**
    * Used to link track scans to a scan station.
    */
-  @OneToMany(() => TrackScan, scan => scan.track)
+  @OneToMany(() => TrackScan, scan => scan.track, { nullable: true })
   scans: TrackScan[];
 }
diff --git a/src/models/Track.ts b/src/models/Track.ts
index ce4693c..ad6f476 100644
--- a/src/models/Track.ts
+++ b/src/models/Track.ts
@@ -41,12 +41,12 @@ export class Track {
   /**
    * Used to link scan stations to track.
    */
-  @OneToMany(() => ScanStation, station => station.track)
+  @OneToMany(() => ScanStation, station => station.track, { nullable: true })
   stations: ScanStation[];
 
   /**
    * Used to link track scans to a track.
    */
-  @OneToMany(() => TrackScan, scan => scan.track)
+  @OneToMany(() => TrackScan, scan => scan.track, { nullable: true })
   scans: TrackScan[];
 }
diff --git a/src/models/TrackScan.ts b/src/models/TrackScan.ts
index ce35ee8..ae0467c 100644
--- a/src/models/TrackScan.ts
+++ b/src/models/TrackScan.ts
@@ -22,21 +22,21 @@ export class TrackScan extends Scan {
    * The associated track.
    */
   @IsNotEmpty()
-  @ManyToOne(() => Track, track => track.scans)
+  @ManyToOne(() => Track, track => track.scans, { nullable: true })
   track: Track;
 
   /**
    * The associated card.
    */
   @IsNotEmpty()
-  @ManyToOne(() => RunnerCard, card => card.scans)
+  @ManyToOne(() => RunnerCard, card => card.scans, { nullable: true })
   card: RunnerCard;
 
   /**
    * The scanning station.
    */
   @IsNotEmpty()
-  @ManyToOne(() => ScanStation, station => station.scans)
+  @ManyToOne(() => ScanStation, station => station.scans, { nullable: true })
   station: ScanStation;
 
   /**
diff --git a/src/models/User.ts b/src/models/User.ts
index fce74e8..3f9a1db 100644
--- a/src/models/User.ts
+++ b/src/models/User.ts
@@ -67,7 +67,7 @@ export class User {
   /**
      * permissions
      */
-  @ManyToOne(() => Permission, permission => permission.users)
+  @ManyToOne(() => Permission, permission => permission.users, { nullable: true })
   permissions: Permission[];
 
   /**
diff --git a/src/models/UserGroup.ts b/src/models/UserGroup.ts
index ae014e2..c3b2f0c 100644
--- a/src/models/UserGroup.ts
+++ b/src/models/UserGroup.ts
@@ -23,7 +23,7 @@ export abstract class UserGroup {
   /**
      * permissions
      */
-  @ManyToOne(() => Permission, permission => permission.groups)
+  @ManyToOne(() => Permission, permission => permission.groups, { nullable: true })
   permissions: Permission[];
 
   /**