diff --git a/src/main/java/de/financer/config/FinancerConfig.java b/src/main/java/de/financer/config/FinancerConfig.java
index f08e8a1..a9371cd 100644
--- a/src/main/java/de/financer/config/FinancerConfig.java
+++ b/src/main/java/de/financer/config/FinancerConfig.java
@@ -1,6 +1,8 @@
 package de.financer.config;
 
 import de.jollyday.HolidayCalendar;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
 import org.springframework.boot.context.properties.ConfigurationProperties;
 import org.springframework.context.annotation.Configuration;
 
@@ -12,6 +14,8 @@ import java.util.Optional;
 @Configuration
 @ConfigurationProperties(prefix = "financer")
 public class FinancerConfig {
+    private static final Logger LOGGER = LoggerFactory.getLogger(FinancerConfig.class);
+
     private String countryCode;
     private String state;
     private String dateFormat;
@@ -33,8 +37,8 @@ public class FinancerConfig {
     }
 
     /**
-     * @return the {@link HolidayCalendar} used to calculate the holidays. Internally uses the country code
-     * specified via {@link FinancerConfig#getCountryCode}.
+     * @return the {@link HolidayCalendar} used to calculate the holidays. Internally uses the country code specified
+     * via {@link FinancerConfig#getCountryCode}.
      */
     public HolidayCalendar getHolidayCalendar() {
         final Optional<HolidayCalendar> optionalHoliday = Arrays.asList(HolidayCalendar.values()).stream()
@@ -42,7 +46,10 @@ public class FinancerConfig {
                                                                 .findFirst();
 
         if (!optionalHoliday.isPresent()) {
-            // TODO log info about default DE
+            LOGGER.warn(String
+                    .format("Use Germany as fallback country for holiday calculations. Configured country code is: %s. " +
+                                    "This does not match any valid country code as specified by Jollyday",
+                            this.countryCode));
         }
 
         return optionalHoliday.orElse(HolidayCalendar.GERMANY);
@@ -57,12 +64,11 @@ public class FinancerConfig {
     }
 
     /**
-     * @return the date format used in e.g. the
-     * {@link de.financer.service.TransactionService#createTransaction(String, String, Long, String, String)
-     * TransactionService#createTransaction} or
-     * {@link de.financer.service.RecurringTransactionService#createRecurringTransaction(String, String, Long, String,
-     * String, String, String, String) RecurringTransactionService#createRecurringTransaction} methods. Used to parse
-     * the client-supplied date string to proper {@link java.time.LocalDate LocalDate} objects
+     * @return the date format used in e.g. the {@link de.financer.service.TransactionService#createTransaction(String,
+     * String, Long, String, String) TransactionService#createTransaction} or {@link
+     * de.financer.service.RecurringTransactionService#createRecurringTransaction(String, String, Long, String, String,
+     * String, String, String) RecurringTransactionService#createRecurringTransaction} methods. Used to parse the
+     * client-supplied date string to proper {@link java.time.LocalDate LocalDate} objects
      */
     public String getDateFormat() {
         return dateFormat;
@@ -71,9 +77,10 @@ public class FinancerConfig {
     public void setDateFormat(String dateFormat) {
         try {
             DateTimeFormatter.ofPattern(dateFormat);
-        }
-        catch (IllegalArgumentException e) {
-            // TODO log info about default dd.MM.yyyy
+        } catch (IllegalArgumentException e) {
+            LOGGER.warn(String
+                    .format("Use 'dd.MM.yyyy' as fallback for the date format because the configured format '%s' " +
+                            "cannot be parsed!", dateFormat), e);
 
             dateFormat = "dd.MM.yyyy";
         }
diff --git a/src/main/java/de/financer/controller/AccountController.java b/src/main/java/de/financer/controller/AccountController.java
index 144efaa..202aeef 100644
--- a/src/main/java/de/financer/controller/AccountController.java
+++ b/src/main/java/de/financer/controller/AccountController.java
@@ -1,7 +1,10 @@
 package de.financer.controller;
 
+import de.financer.ResponseReason;
 import de.financer.model.Account;
 import de.financer.service.AccountService;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
 import org.springframework.beans.factory.annotation.Autowired;
 import org.springframework.http.ResponseEntity;
 import org.springframework.web.bind.annotation.RequestMapping;
@@ -11,6 +14,8 @@ import org.springframework.web.bind.annotation.RestController;
 @RequestMapping("accounts")
 public class AccountController {
 
+    private static final Logger LOGGER = LoggerFactory.getLogger(AccountController.class);
+
     @Autowired
     private AccountService accountService;
 
@@ -36,6 +41,16 @@ public class AccountController {
 
     @RequestMapping("createAccount")
     public ResponseEntity createAccount(String key, String type) {
-        return this.accountService.createAccount(key, type).toResponseEntity();
+        if (LOGGER.isDebugEnabled()) {
+            LOGGER.debug(String.format("/accounts/createAccount got parameters: %s, %s", key, type));
+        }
+
+        final ResponseReason responseReason = this.accountService.createAccount(key, type);
+
+        if (LOGGER.isDebugEnabled()) {
+            LOGGER.debug(String.format("/accounts/createAccount returns with %s", responseReason.name()));
+        }
+
+        return responseReason.toResponseEntity();
     }
 }
diff --git a/src/main/java/de/financer/controller/RecurringTransactionController.java b/src/main/java/de/financer/controller/RecurringTransactionController.java
index 62feb32..cd78932 100644
--- a/src/main/java/de/financer/controller/RecurringTransactionController.java
+++ b/src/main/java/de/financer/controller/RecurringTransactionController.java
@@ -1,7 +1,10 @@
 package de.financer.controller;
 
+import de.financer.ResponseReason;
 import de.financer.model.RecurringTransaction;
 import de.financer.service.RecurringTransactionService;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
 import org.springframework.beans.factory.annotation.Autowired;
 import org.springframework.http.ResponseEntity;
 import org.springframework.web.bind.annotation.RequestMapping;
@@ -13,6 +16,8 @@ import java.util.Optional;
 @RequestMapping("recurringTransactions")
 public class RecurringTransactionController {
 
+    private static final Logger LOGGER = LoggerFactory.getLogger(RecurringTransactionController.class);
+
     @Autowired
     private RecurringTransactionService recurringTransactionService;
 
@@ -35,17 +40,44 @@ public class RecurringTransactionController {
     public ResponseEntity createRecurringTransaction(String fromAccountKey, String toAccountKey, Long amount,
                                                      String description, String holidayWeekendType,
                                                      String intervalType, String firstOccurrence,
-                                                     String lastOccurrence) {
-        return this.recurringTransactionService.createRecurringTransaction(fromAccountKey, toAccountKey, amount,
-                                                                           description, holidayWeekendType,
-                                                                           intervalType, firstOccurrence,
-                                                                           lastOccurrence)
-                                               .toResponseEntity();
+                                                     String lastOccurrence
+    ) {
+        if (LOGGER.isDebugEnabled()) {
+            LOGGER.debug(String
+                    .format("/recurringTransactions/createRecurringTransaction got parameters: %s, %s, %s, %s, %s, " +
+                                    "%s, %s, %s", fromAccountKey, toAccountKey, amount, description, holidayWeekendType,
+                            intervalType, firstOccurrence, lastOccurrence));
+        }
+
+        final ResponseReason responseReason = this.recurringTransactionService
+                .createRecurringTransaction(fromAccountKey, toAccountKey, amount, description, holidayWeekendType,
+                        intervalType, firstOccurrence, lastOccurrence);
+
+        if (LOGGER.isDebugEnabled()) {
+            LOGGER.debug(String
+                    .format("/recurringTransactions/createRecurringTransaction returns with %s", responseReason
+                            .name()));
+        }
+
+        return responseReason.toResponseEntity();
     }
 
     @RequestMapping("createTransaction")
     public ResponseEntity createTransaction(String recurringTransactionId, Long amount) {
-        return this.recurringTransactionService.createTransaction(recurringTransactionId, Optional.ofNullable(amount))
-                                               .toResponseEntity();
+        if (LOGGER.isDebugEnabled()) {
+            LOGGER.debug(String
+                    .format("/recurringTransactions/createTransaction got parameters: %s, %s",
+                            recurringTransactionId, amount));
+        }
+
+        final ResponseReason responseReason = this.recurringTransactionService
+                .createTransaction(recurringTransactionId, Optional.ofNullable(amount));
+
+        if (LOGGER.isDebugEnabled()) {
+            LOGGER.debug(String
+                    .format("/recurringTransactions/createTransaction returns with %s", responseReason.name()));
+        }
+
+        return responseReason.toResponseEntity();
     }
 }
diff --git a/src/main/java/de/financer/controller/TransactionController.java b/src/main/java/de/financer/controller/TransactionController.java
index bb14c44..8ddbb58 100644
--- a/src/main/java/de/financer/controller/TransactionController.java
+++ b/src/main/java/de/financer/controller/TransactionController.java
@@ -1,7 +1,10 @@
 package de.financer.controller;
 
+import de.financer.ResponseReason;
 import de.financer.model.Transaction;
 import de.financer.service.TransactionService;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
 import org.springframework.beans.factory.annotation.Autowired;
 import org.springframework.http.ResponseEntity;
 import org.springframework.web.bind.annotation.RequestMapping;
@@ -10,6 +13,8 @@ import org.springframework.web.bind.annotation.RestController;
 @RestController
 @RequestMapping("transactions")
 public class TransactionController {
+    private static final Logger LOGGER = LoggerFactory.getLogger(TransactionController.class);
+
     @Autowired
     private TransactionService transactionService;
 
@@ -25,8 +30,21 @@ public class TransactionController {
 
     @RequestMapping(value = "createTransaction")
     public ResponseEntity createTransaction(String fromAccountKey, String toAccountKey, Long amount, String date,
-                                            String description) {
-        return this.transactionService.createTransaction(fromAccountKey, toAccountKey, amount, date, description)
-                                      .toResponseEntity();
+                                            String description
+    ) {
+        if (LOGGER.isDebugEnabled()) {
+            LOGGER.debug(String
+                    .format("/transactions/createTransaction got parameters: %s, %s, %s, %s, %s",
+                            fromAccountKey, toAccountKey, amount, date, description));
+        }
+
+        final ResponseReason responseReason = this.transactionService
+                .createTransaction(fromAccountKey, toAccountKey, amount, date, description);
+
+        if (LOGGER.isDebugEnabled()) {
+            LOGGER.debug(String.format("/transactions/createTransaction returns with %s", responseReason.name()));
+        }
+
+        return responseReason.toResponseEntity();
     }
 }
diff --git a/src/main/java/de/financer/service/AccountService.java b/src/main/java/de/financer/service/AccountService.java
index 694988e..7f05956 100644
--- a/src/main/java/de/financer/service/AccountService.java
+++ b/src/main/java/de/financer/service/AccountService.java
@@ -6,6 +6,8 @@ import de.financer.model.Account;
 import de.financer.model.AccountStatus;
 import de.financer.model.AccountType;
 import org.apache.commons.lang3.StringUtils;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
 import org.springframework.beans.factory.annotation.Autowired;
 import org.springframework.stereotype.Service;
 import org.springframework.transaction.annotation.Propagation;
@@ -16,6 +18,8 @@ import java.util.stream.Collectors;
 
 @Service
 public class AccountService {
+    private static final Logger LOGGER = LoggerFactory.getLogger(AccountService.class);
+
     @Autowired
     private AccountRepository accountRepository;
 
@@ -95,7 +99,8 @@ public class AccountService {
             this.accountRepository.save(account);
         }
         catch (Exception e) {
-            // TODO log and check for unique constraint exception so we can return a more specific error
+            LOGGER.error(String.format("Could not save account %s|%s", key, type), e);
+
             return ResponseReason.UNKNOWN_ERROR;
         }
 
diff --git a/src/main/java/de/financer/service/RecurringTransactionService.java b/src/main/java/de/financer/service/RecurringTransactionService.java
index 1e6b00e..6eb27ce 100644
--- a/src/main/java/de/financer/service/RecurringTransactionService.java
+++ b/src/main/java/de/financer/service/RecurringTransactionService.java
@@ -10,6 +10,8 @@ import de.financer.model.RecurringTransaction;
 import org.apache.commons.collections4.IterableUtils;
 import org.apache.commons.lang3.StringUtils;
 import org.apache.commons.lang3.math.NumberUtils;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
 import org.springframework.beans.factory.annotation.Autowired;
 import org.springframework.stereotype.Service;
 import org.springframework.transaction.annotation.Propagation;
@@ -24,6 +26,7 @@ import java.util.stream.Collectors;
 
 @Service
 public class RecurringTransactionService {
+    private static final Logger LOGGER = LoggerFactory.getLogger(RecurringTransactionService.class);
 
     @Autowired
     private RecurringTransactionRepository recurringTransactionRepository;
@@ -48,6 +51,8 @@ public class RecurringTransactionService {
         final Account account = this.accountService.getAccountByKey(accountKey);
 
         if (account == null) {
+            LOGGER.warn(String.format("Account with key %s not found!", accountKey));
+
             return Collections.emptyList();
         }
 
@@ -250,8 +255,7 @@ public class RecurringTransactionService {
 
             response = ResponseReason.OK;
         } catch (Exception e) {
-            // TODO log
-            e.printStackTrace();
+            LOGGER.error("Could not create recurring transaction!", e);
 
             response = ResponseReason.UNKNOWN_ERROR;
         }
diff --git a/src/main/java/de/financer/service/RuleService.java b/src/main/java/de/financer/service/RuleService.java
index 7dee141..35436bc 100644
--- a/src/main/java/de/financer/service/RuleService.java
+++ b/src/main/java/de/financer/service/RuleService.java
@@ -6,6 +6,8 @@ import de.financer.model.AccountType;
 import de.financer.model.IntervalType;
 import de.jollyday.HolidayManager;
 import de.jollyday.ManagerParameters;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
 import org.springframework.beans.factory.InitializingBean;
 import org.springframework.beans.factory.annotation.Autowired;
 import org.springframework.stereotype.Service;
@@ -18,13 +20,12 @@ import java.util.*;
 import static de.financer.model.AccountType.*;
 
 /**
- * This service encapsulates methods that form basic logic rules.
- * While most of the logic could be placed elsewhere this service provides
- * centralized access to these rules. Placing them in here also enables easy
- * unit testing.
+ * This service encapsulates methods that form basic logic rules. While most of the logic could be placed elsewhere this
+ * service provides centralized access to these rules. Placing them in here also enables easy unit testing.
  */
 @Service
 public class RuleService implements InitializingBean {
+    private static final Logger LOGGER = LoggerFactory.getLogger(RuleService.class);
 
     @Autowired
     private FinancerConfig financerConfig;
@@ -65,10 +66,11 @@ public class RuleService implements InitializingBean {
     /**
      * This method returns the multiplier for the given from account.
      * <p>
-     * The multiplier controls whether the current amount of the given from account is increased or
-     * decreased depending on the {@link AccountType} of the given account.
+     * The multiplier controls whether the current amount of the given from account is increased or decreased depending
+     * on the {@link AccountType} of the given account.
      *
      * @param fromAccount the from account to get the multiplier for
+     *
      * @return the multiplier, either <code>1</code> or <code>-1</code>
      */
     public long getMultiplierFromAccount(Account fromAccount) {
@@ -89,16 +91,20 @@ public class RuleService implements InitializingBean {
             return 1L;
         }
 
+        LOGGER.warn(String
+                .format("Unknown or invalid account type in getMultiplierFromAccount: %s", accountType.name()));
+
         return 1L;
     }
 
     /**
      * This method returns the multiplier for the given to account.
      * <p>
-     * The multiplier controls whether the current amount of the given to account is increased or
-     * decreased depending on the {@link AccountType} of the given account.
+     * The multiplier controls whether the current amount of the given to account is increased or decreased depending on
+     * the {@link AccountType} of the given account.
      *
      * @param toAccount the to account to get the multiplier for
+     *
      * @return the multiplier, either <code>1</code> or <code>-1</code>
      */
     public long getMultiplierToAccount(Account toAccount) {
@@ -117,27 +123,33 @@ public class RuleService implements InitializingBean {
             return 1L;
         }
 
+        LOGGER.warn(String
+                .format("Unknown or invalid account type in getMultiplierToAccount: %s", accountType.name()));
+
         return -1L;
     }
 
     /**
-     * This method validates whether the booking from <code>fromAccount</code> to <code>toAccount</code>
-     * is valid, e.g. booking directly from an {@link AccountType#INCOME INCOME} to an {@link AccountType#EXPENSE EXPENSE}
-     * account does not make sense and is declared as invalid.
+     * This method validates whether the booking from <code>fromAccount</code> to <code>toAccount</code> is valid, e.g.
+     * booking directly from an {@link AccountType#INCOME INCOME} to an {@link AccountType#EXPENSE EXPENSE} account does
+     * not make sense and is declared as invalid.
      *
      * @param fromAccount the account to subtract the money from
-     * @param toAccount   the account to add the money to
-     * @return <code>true</code> if the from-&gt;to relationship of the given accounts is valid, <code>false</code> otherwise
+     * @param toAccount the account to add the money to
+     *
+     * @return <code>true</code> if the from-&gt;to relationship of the given accounts is valid, <code>false</code>
+     * otherwise
      */
     public boolean isValidBooking(Account fromAccount, Account toAccount) {
         return this.bookingRules.get(fromAccount.getType()).contains(toAccount.getType());
     }
 
     /**
-     * This method gets the {@link Period} for the given {@link IntervalType},
-     * e.g. a period of three months for {@link IntervalType#QUARTERLY}.
+     * This method gets the {@link Period} for the given {@link IntervalType}, e.g. a period of three months for {@link
+     * IntervalType#QUARTERLY}.
      *
      * @param intervalType to get the period for
+     *
      * @return the period matching the interval type
      */
     public Period getPeriodForInterval(IntervalType intervalType) {
@@ -148,18 +160,24 @@ public class RuleService implements InitializingBean {
      * This method checks whether the given date is a holiday in the configured country and state.
      *
      * @param now the date to check
+     *
      * @return <code>true</code> if the given date is a holiday, <code>false</code> otherwise
      */
     public boolean isHoliday(LocalDate now) {
+        if (LOGGER.isDebugEnabled()) {
+            LOGGER.debug(String.format("Use state '%s' for holiday calculation", this.financerConfig.getState()));
+        }
+
         return HolidayManager.getInstance(ManagerParameters.create(this.financerConfig.getHolidayCalendar()))
                              .isHoliday(now, this.financerConfig.getState());
     }
 
     /**
-     * This method checks whether the given date is a weekend day, i.e. whether it's a
-     * {@link DayOfWeek#SATURDAY} or {@link DayOfWeek#SUNDAY}.
+     * This method checks whether the given date is a weekend day, i.e. whether it's a {@link DayOfWeek#SATURDAY} or
+     * {@link DayOfWeek#SUNDAY}.
      *
      * @param now the date to check
+     *
      * @return <code>true</code> if the given date is a weekend day, <code>false</code> otherwise
      */
     public boolean isWeekend(LocalDate now) {
diff --git a/src/main/java/de/financer/service/TransactionService.java b/src/main/java/de/financer/service/TransactionService.java
index ff49233..84ad9aa 100644
--- a/src/main/java/de/financer/service/TransactionService.java
+++ b/src/main/java/de/financer/service/TransactionService.java
@@ -6,6 +6,8 @@ import de.financer.dba.TransactionRepository;
 import de.financer.model.Account;
 import de.financer.model.RecurringTransaction;
 import de.financer.model.Transaction;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
 import org.springframework.beans.factory.annotation.Autowired;
 import org.springframework.stereotype.Service;
 import org.springframework.transaction.annotation.Propagation;
@@ -18,6 +20,8 @@ import java.util.Collections;
 
 @Service
 public class TransactionService {
+    private static final Logger LOGGER = LoggerFactory.getLogger(TransactionService.class);
+
     @Autowired
     private AccountService accountService;
 
@@ -47,6 +51,8 @@ public class TransactionService {
         final Account account = this.accountService.getAccountByKey(accountKey);
 
         if (account == null) {
+            LOGGER.warn(String.format("Account with key %s not found!", accountKey));
+
             return Collections.emptyList();
         }
 
@@ -89,7 +95,7 @@ public class TransactionService {
 
             response = ResponseReason.OK;
         } catch (Exception e) {
-            // TODO log
+            LOGGER.error("Could not create transaction!", e);
 
             response = ResponseReason.UNKNOWN_ERROR;
         }
diff --git a/src/main/java/de/financer/task/SendRecurringTransactionReminderTask.java b/src/main/java/de/financer/task/SendRecurringTransactionReminderTask.java
index 124379b..4e003d8 100644
--- a/src/main/java/de/financer/task/SendRecurringTransactionReminderTask.java
+++ b/src/main/java/de/financer/task/SendRecurringTransactionReminderTask.java
@@ -4,6 +4,8 @@ import de.financer.config.FinancerConfig;
 import de.financer.model.RecurringTransaction;
 import de.financer.service.RecurringTransactionService;
 import org.apache.commons.collections4.IterableUtils;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
 import org.springframework.beans.factory.annotation.Autowired;
 import org.springframework.mail.MailException;
 import org.springframework.mail.SimpleMailMessage;
@@ -14,6 +16,8 @@ import org.springframework.stereotype.Component;
 @Component
 public class SendRecurringTransactionReminderTask {
 
+    private static final Logger LOGGER = LoggerFactory.getLogger(SendRecurringTransactionReminderTask.class);
+
     @Autowired
     private RecurringTransactionService recurringTransactionService;
 
@@ -25,13 +29,23 @@ public class SendRecurringTransactionReminderTask {
 
     @Scheduled(cron = "0 30 0 * * *")
     public void sendReminder() {
+        if (LOGGER.isDebugEnabled()) {
+            LOGGER.debug("Enter recurring transaction reminder task");
+        }
+
         final Iterable<RecurringTransaction> recurringTransactions = this.recurringTransactionService.getAllDueToday();
 
         // If no recurring transaction is due today we don't need to send a reminder
         if (IterableUtils.isEmpty(recurringTransactions)) {
+            LOGGER.info("No recurring transactions due today!");
+
             return; // early return
         }
 
+        LOGGER.info(String
+                .format("%s recurring transaction are due today and are about to be included in the reminder email",
+                        IterableUtils.size(recurringTransactions)));
+
         final StringBuilder reminderBuilder = new StringBuilder();
 
         reminderBuilder.append("The following recurring transactions are due today:")
@@ -63,7 +77,10 @@ public class SendRecurringTransactionReminderTask {
         try {
             this.mailSender.send(msg);
         } catch (MailException e) {
-            // TODO log
+            LOGGER.error("Could not send recurring transaction email reminder!", e);
+
+            LOGGER.info("Dumb email reminder content because the sending failed");
+            LOGGER.info(reminderBuilder.toString());
         }
     }
 }
diff --git a/src/main/resources/config/application.properties b/src/main/resources/config/application.properties
index c4701ea..cfaaa4c 100644
--- a/src/main/resources/config/application.properties
+++ b/src/main/resources/config/application.properties
@@ -14,6 +14,8 @@ info.build.group=@project.groupId@
 info.build.artifact=@project.artifactId@
 info.build.version=@project.version@
 
+logging.level.de.financer=DEBUG
+
 # Country code for holiday checks
 # Mostly an uppercase ISO 3166 2-letter code
 # For a complete list of the supported codes see https://github.com/svendiedrichsen/jollyday/blob/master/src/main/java/de/jollyday/HolidayCalendar.java