diff --git a/api/api.go b/api/api.go
index cd30c6b..2d43e84 100644
--- a/api/api.go
+++ b/api/api.go
@@ -98,6 +98,9 @@ func (a *API) initRouter() http.Handler {
 		// refresh the token
 		log.Infow("new route", "method", "POST", "path", authRefresTokenEndpoint)
 		r.Post(authRefresTokenEndpoint, a.refreshTokenHandler)
+		// writable organization addresses
+		log.Infow("new route", "method", "GET", "path", authAddressesEndpoint)
+		r.Get(authAddressesEndpoint, a.writableOrganizationAddressesHandler)
 		// get user information
 		log.Infow("new route", "method", "GET", "path", myUsersEndpoint)
 		r.Get(myUsersEndpoint, a.userInfoHandler)
diff --git a/api/auth.go b/api/auth.go
index 3285792..751b48a 100644
--- a/api/auth.go
+++ b/api/auth.go
@@ -59,3 +59,37 @@ func (a *API) authLoginHandler(w http.ResponseWriter, r *http.Request) {
 	// send the token back to the user
 	httpWriteJSON(w, res)
 }
+
+// writableOrganizationAddressesHandler returns the list of addresses of the
+// organizations where the user has write access.
+func (a *API) writableOrganizationAddressesHandler(w http.ResponseWriter, r *http.Request) {
+	// get the user from the request context
+	user, ok := userFromContext(r.Context())
+	if !ok {
+		ErrUnauthorized.Write(w)
+		return
+	}
+	// check if the user has organizations
+	if len(user.Organizations) == 0 {
+		ErrNoOrganizations.Write(w)
+	}
+	// get the user organizations information from the database if any
+	userAddresses := &OrganizationAddresses{
+		Addresses: []string{},
+	}
+	// get the addresses of the organizations where the user has write access
+	for _, org := range user.Organizations {
+		// check if the user has write access to the organization based on the
+		// role of the user in the organization
+		if db.HasWriteAccess(org.Role) {
+			userAddresses.Addresses = append(userAddresses.Addresses, org.Address)
+		}
+	}
+	res, err := json.Marshal(userAddresses)
+	if err != nil {
+		ErrGenericInternalServerError.Write(w)
+		return
+	}
+	// Send the token back to the user
+	httpWriteJSON(w, res)
+}
diff --git a/api/docs.md b/api/docs.md
index 6a0022c..236e27e 100644
--- a/api/docs.md
+++ b/api/docs.md
@@ -74,6 +74,33 @@
 | `401` | `40001` | `user not authorized` |
 | `500` | `50002` | `internal server error` |
 
+### 💼 User writable organizations addresses
+This endpoint only returns the addresses of the organizations where the current user (identified by the JWT) has a role with write permission.
+
+* **Path** `/auth/addresses`
+* **Method** `GET`
+* **Headers**
+  * `Authentication: Bearer <user_token>`
+
+* **Response**
+```json
+{
+  "addresses": [
+    "0x0000000001",
+    "0x0000000002",
+    "0x0000000003",
+  ]
+}
+```
+
+* **Errors**
+
+| HTTP Status | Error code | Message |
+|:---:|:---:|:---|
+| `401` | `40001` | `user not authorized` |
+| `404` | `40012` | `this user has not been assigned to any organization` |
+| `500` | `50002` | `internal server error` |
+
 ## 👥 Users
 
 ### 🙋 Register
@@ -314,11 +341,17 @@ Only the following parameters can be changed. Every parameter is optional.
 * **Method** `POST`
 * **Headers**
   * `Authentication: Bearer <user_token>`
+* **Request body**
+```json
+{
+  "address": "0x...",
+  "txPayload": "<base64_encoded_protobuf>"
+}
+```
 
 * **Response**
 ```json
 {
-  "organizationAddress": "0x...",
   "txPayload": "<base64_encoded_protobuf>"
 }
 ```
@@ -341,11 +374,17 @@ Only the following parameters can be changed. Every parameter is optional.
 * **Method** `POST`
 * **Headers**
   * `Authentication: Bearer <user_token>`
+* **Request body**
+```json
+{
+  "address": "0x...",
+  "payload": "<payload_to_sign>"
+}
+```
 
 * **Response**
 ```json
 {
-  "organizationAddress": "0x...",
   "payload": "<payload_to_sign>"
 }
 ```
diff --git a/api/errors_definition.go b/api/errors_definition.go
index 359575b..f8fb2ad 100644
--- a/api/errors_definition.go
+++ b/api/errors_definition.go
@@ -37,6 +37,7 @@ var (
 	ErrOrganizationNotFound    = Error{Code: 40009, HTTPstatus: http.StatusNotFound, Err: fmt.Errorf("organization not found")}
 	ErrMalformedURLParam       = Error{Code: 40010, HTTPstatus: http.StatusBadRequest, Err: fmt.Errorf("malformed URL parameter")}
 	ErrNoOrganizationProvided  = Error{Code: 40011, HTTPstatus: http.StatusBadRequest, Err: fmt.Errorf("no organization provided")}
+	ErrNoOrganizations         = Error{Code: 40012, HTTPstatus: http.StatusNotFound, Err: fmt.Errorf("this user has not been assigned to any organization")}
 
 	ErrMarshalingServerJSONFailed  = Error{Code: 50001, HTTPstatus: http.StatusInternalServerError, Err: fmt.Errorf("marshaling (server-side) JSON failed")}
 	ErrGenericInternalServerError  = Error{Code: 50002, HTTPstatus: http.StatusInternalServerError, Err: fmt.Errorf("internal server error")}
diff --git a/api/routes.go b/api/routes.go
index a372f2d..86fe3da 100644
--- a/api/routes.go
+++ b/api/routes.go
@@ -7,6 +7,8 @@ const (
 	authRefresTokenEndpoint = "/auth/refresh"
 	// POST /auth/login to login and get a JWT token
 	authLoginEndpoint = "/auth/login"
+	// GET /auth/addresses to get the writable organization addresses
+	authAddressesEndpoint = "/auth/addresses"
 
 	// user routes
 
diff --git a/api/transaction.go b/api/transaction.go
index 1ac9ef8..e37a1f4 100644
--- a/api/transaction.go
+++ b/api/transaction.go
@@ -30,13 +30,13 @@ func (a *API) signTxHandler(w http.ResponseWriter, r *http.Request) {
 		return
 	}
 	// check if the user has the admin role for the organization
-	if !user.HasRoleFor(signReq.OrganizationAddress, db.AdminRole) {
+	if !user.HasRoleFor(signReq.Address, db.AdminRole) {
 		ErrUnauthorized.With("user does not have admin role").Write(w)
 		return
 	}
 	// get the organization info from the database with the address provided in
 	// the request
-	org, _, err := a.db.Organization(signReq.OrganizationAddress, false)
+	org, _, err := a.db.Organization(signReq.Address, false)
 	if err != nil {
 		if err == db.ErrNotFound {
 			ErrOrganizationNotFound.Withf("organization not found").Write(w)
@@ -147,13 +147,13 @@ func (a *API) signMessageHandler(w http.ResponseWriter, r *http.Request) {
 		return
 	}
 	// check if the user has the admin role for the organization
-	if !user.HasRoleFor(signReq.OrganizationAddress, db.AdminRole) {
+	if !user.HasRoleFor(signReq.Address, db.AdminRole) {
 		ErrUnauthorized.With("user does not have admin role").Write(w)
 		return
 	}
 	// get the organization info from the database with the address provided in
 	// the request
-	org, _, err := a.db.Organization(signReq.OrganizationAddress, false)
+	org, _, err := a.db.Organization(signReq.Address, false)
 	if err != nil {
 		if err == db.ErrNotFound {
 			ErrOrganizationNotFound.Withf("organization not found").Write(w)
diff --git a/api/types.go b/api/types.go
index e30d719..52ccfd3 100644
--- a/api/types.go
+++ b/api/types.go
@@ -23,6 +23,12 @@ type OrganizationInfo struct {
 	Parent      *OrganizationInfo `json:"parent"`
 }
 
+// OrganizationAddresses is the struct that represents a list of addresses of
+// organizations in the API.
+type OrganizationAddresses struct {
+	Addresses []string `json:"addresses"`
+}
+
 // UserOrganization is the struct that represents the organization of a user in
 // the API, including the role of the user in the organization.
 type UserOrganization struct {
@@ -53,16 +59,16 @@ type LoginResponse struct {
 // TransactionData is the struct that contains the data of a transaction to
 // be signed, but also is used to return the signed transaction.
 type TransactionData struct {
-	OrganizationAddress string `json:"organizationAddress"`
-	TxPayload           string `json:"txPayload"`
+	Address   string `json:"address"`
+	TxPayload string `json:"txPayload"`
 }
 
 // MessageSignature is the struct that contains the payload and the signature.
 // Its used to receive and return a signed message.
 type MessageSignature struct {
-	OrganizationAddress string         `json:"organizationAddress"`
-	Payload             []byte         `json:"payload,omitempty"`
-	Signature           types.HexBytes `json:"signature,omitempty"`
+	Address   string         `json:"address"`
+	Payload   []byte         `json:"payload,omitempty"`
+	Signature types.HexBytes `json:"signature,omitempty"`
 }
 
 // organizationFromDB converts a db.Organization to an OrganizationInfo, if the parent
diff --git a/db/const.go b/db/const.go
index 8473a0a..bcbe36c 100644
--- a/db/const.go
+++ b/db/const.go
@@ -10,11 +10,25 @@ const (
 	CommunityType OrganizationType = "community"
 )
 
+// writableRoles is a map that contains if the role is writable or not
+var writableRoles = map[UserRole]bool{
+	AdminRole:   true,
+	ManagerRole: true,
+	ViewerRole:  false,
+}
+
+// HasWriteAccess function checks if the user role has write access
+func HasWriteAccess(role UserRole) bool {
+	return writableRoles[role]
+}
+
+// validOrganizationTypes is a map that contains the valid organization types
 var validOrganizationTypes = map[OrganizationType]bool{
 	CompanyType:   true,
 	CommunityType: true,
 }
 
+// IsOrganizationTypeValid function checks if the organization type is valid
 func IsOrganizationTypeValid(ot string) bool {
 	_, valid := validOrganizationTypes[OrganizationType(ot)]
 	return valid
diff --git a/db/types.go b/db/types.go
index 5260c72..36c2db3 100644
--- a/db/types.go
+++ b/db/types.go
@@ -1,10 +1,6 @@
 package db
 
-import (
-	"time"
-
-	"go.vocdoni.io/dvote/log"
-)
+import "time"
 
 type User struct {
 	ID            uint64               `json:"id" bson:"_id"`
@@ -16,7 +12,6 @@ type User struct {
 
 func (u *User) HasRoleFor(address string, role UserRole) bool {
 	for _, org := range u.Organizations {
-		log.Info(org.Address == address, org.Role == role)
 		if org.Address == address && string(org.Role) == string(role) {
 			return true
 		}
diff --git a/db/users.go b/db/users.go
index 28ed7a1..4346e8e 100644
--- a/db/users.go
+++ b/db/users.go
@@ -172,9 +172,9 @@ func (ms *MongoStorage) IsMemberOf(userEmail, organizationAddress string, role U
 		return false, err
 	}
 	for _, org := range user.Organizations {
-		if org.Address == organizationAddress && org.Role == role {
-			return true, nil
+		if org.Address == organizationAddress {
+			return org.Role == role, nil
 		}
 	}
-	return false, nil
+	return false, ErrNotFound
 }