diff --git a/NAMESPACE b/NAMESPACE
index df6995a..caef0a0 100644
--- a/NAMESPACE
+++ b/NAMESPACE
@@ -43,6 +43,11 @@ export(w2_enforce_streaming)
 export(w2_rename_cols)
 export(w3_enforce_streaming)
 export(w3_rename_cols)
+export(w4_check_skip_logic)
+export(w4_clean_departments)
+export(w4_enforce_skip_logic)
+export(w4_enforce_streaming)
+export(w4_rename_cols)
 export(wrap_outputs)
 importFrom(dplyr,across)
 importFrom(dplyr,all_of)
diff --git a/R/ingest.R b/R/ingest.R
index ca0ab0b..6076bce 100644
--- a/R/ingest.R
+++ b/R/ingest.R
@@ -52,7 +52,7 @@ get_tidy_data_file <- function(...) {
 
 #' @return the exported data as a dataframe
 
-ingest <- function(survey = "1167489",
+ingest <- function(survey = "1376897",
                    token = Sys.getenv("CARS_TOKEN"),
                    secret = Sys.getenv("CARS_SECRET"),
                    proxies = Sys.getenv("alt_proxy"),
@@ -199,10 +199,12 @@ get_all_waves <- function(mode = c("api", "file")) {
 
   if (mode == "api") {
     data <- get_tidy_data_api()
+    w4_data <- get_tidy_data_api(survey = "1167489")
     w3_data <- get_tidy_data_api(survey = "961613")
     w2_data <- get_tidy_data_api(survey = "790800")
   } else if (mode == "file") {
     data <- read_file("2022_data.csv")
+    w4_data <- read_file("2022_data.csv")
     w3_data <- read_file("2021_data.csv")
     w2_data <- read_file("2020_data.csv")
   }
@@ -213,7 +215,14 @@ get_all_waves <- function(mode = c("api", "file")) {
     apply_skip_logic() %>%
     clean_departments() %>%
     derive_vars()
-  data$year <- 2022
+  data$year <- 2023
+
+  w4_data <- w4_data %>%
+    tidy_colnames() %>%
+    w4_rename_cols() %>%
+    w4_enforce_streaming() %>%
+    w4_clean_departments()
+  w4_data$year <- 2022
 
   w3_data <- w3_data %>%
     tidy_colnames() %>%
@@ -227,7 +236,7 @@ get_all_waves <- function(mode = c("api", "file")) {
     w2_enforce_streaming()
   w2_data$year <- 2020
 
-  data <- dplyr::bind_rows(data, w3_data, w2_data)
+  data <- dplyr::bind_rows(data, w4_data, w3_data, w2_data)
 
   return(data)
 }
diff --git a/R/wave_2_preprocessing.R b/R/wave_2_preprocessing.R
index 988ed2d..0c96682 100644
--- a/R/wave_2_preprocessing.R
+++ b/R/wave_2_preprocessing.R
@@ -1,8 +1,8 @@
-#' Rename columns (wave 3)
+#' Rename columns (wave 2)
 #'
 #' @description add meaningful column names to dataset ingested from smartsurvey API.
 #'
-#' @param data CARS wave 3 (2021) survey data (data.frame).
+#' @param data CARS wave 2 (2020) survey data (data.frame).
 #'
 #' @return data.frame
 #'
diff --git a/R/wave_4_preprocessing.R b/R/wave_4_preprocessing.R
new file mode 100644
index 0000000..e3673fe
--- /dev/null
+++ b/R/wave_4_preprocessing.R
@@ -0,0 +1,253 @@
+
+#' @title Rename columns
+#'
+#' @description Renames columns and removes unnecessary columns
+#'
+#' @param data tidy CARS dataset
+#'
+#' @return data.frame
+#'
+#' @export
+
+w4_rename_cols <- function(data) {
+
+  if (class(data) != "data.frame") {
+    stop("Unexpected input: data is not a data.frame.")
+  }
+  if (ncol(data) != 112) {
+    stop("Unexpected input: incorrect number of columns. Please use the 2022 CARS dataset.")
+  }
+
+  colnames(data)[c(1, 7:ncol(data))] <- c(
+    "ID",
+    "started",
+    "ended",
+    "tracking_link",
+    "workplace",
+    "CS_grade",
+    "department",
+    "other_department_name",
+    "prof_DS",
+    "prof_DDAT",
+    "prof_GAD",
+    "prof_GES",
+    "prof_geog",
+    "prof_GORS",
+    "prof_GSR",
+    "prof_GSG",
+    "prof_CS_none",
+    "prof_CS_other",
+    "ONS_directorate",
+    "highest_qualification",
+    "qual_1_subject",
+    "qual_1_level",
+    "qual_1_learn_code",
+    "qual_2_subject",
+    "qual_2_level",
+    "qual_2_learn_code",
+    "qual_3_subject",
+    "qual_3_level",
+    "qual_3_learn_code",
+    "code_freq",
+    "management",
+    "ops_analysis",
+    "ops_cleaning",
+    "ops_linking",
+    "ops_transfer_migration",
+    "ops_vis",
+    "ops_machine_learning",
+    "ops_modelling",
+    "ops_QA",
+    "ops_other",
+    "ops_other_name",
+    "knowledge_R",
+    "access_R",
+    "knowledge_SQL",
+    "access_SQL",
+    "knowledge_SAS",
+    "access_SAS",
+    "knowledge_VBA",
+    "access_VBA",
+    "knowledge_python",
+    "access_python",
+    "knowledge_SPSS",
+    "access_SPSS",
+    "knowledge_stata",
+    "access_stata",
+    "knowledge_JS",
+    "access_JS",
+    "knowledge_java",
+    "access_java",
+    "knowledge_C",
+    "access_C",
+    "knowledge_matlab",
+    "access_matlab",
+    "knowledge_access_other",
+    "knowledge_git",
+    "access_git",
+    "other_coding_experience",
+    "coding_ability_change",
+    "prev_coding_experience",
+    "first_learned",
+    "heard_of_RAP",
+    "know_RAP_champ",
+    "strategy_knowledge",
+    "RAP_confident",
+    "RAP_supported",
+    "RAP_resources",
+    "RAP_components",
+    "RAP_important",
+    "RAP_implementing",
+    "RAP_planning",
+    "RAP_comments",
+    "prac_use_open_source",
+    "prac_open_source_own",
+    "prac_version_control",
+    "prac_review",
+    "prac_functions",
+    "prac_unit_test",
+    "prac_package",
+    "prac_dir_structure",
+    "prac_style",
+    "prac_automated_QA",
+    "prac_AQUA_book",
+    "doc_comments",
+    "doc_functions",
+    "doc_readme",
+    "doc_desk_notes",
+    "doc_registers",
+    "doc_AQA_logs",
+    "doc_flow_charts",
+    "doc_other",
+    "CI",
+    "dep_management",
+    "reproducible_workflow",
+    "misc_coding",
+    "misc_support",
+    "misc_additional_data",
+    "misc_other"
+  )
+
+  data <- data[!colnames(data) %in% c("UserNo", "Name", "Email", "IP.Address", "Unique.ID")]
+
+  return(data)
+}
+
+#' @title Clean department data
+#'
+#' @description add NHS to department list and merge departments where needed.
+#'
+#' @param data cleaned CARS dataset
+#'
+#' @return CARS dataset
+#' @export
+
+w4_clean_departments <- function(data) {
+
+  data$department[grepl("forest research", tolower(data$other_department_name))] <- "Forestry Commission"
+
+  data$department[data$workplace == "NHS"] <- "NHS"
+
+  defra_orgs <- c(
+    "Department for Environment, Food and Rural Affairs (excl. agencies)",
+    "Forestry Commission",
+    "Animal and Plant Health Agency",
+    "Centre for Environment, Fisheries and Aquaculture Science",
+    "Rural Payments Agency",
+    "Environment Agency",
+    "Marine Management Organisation",
+    "Natural England"
+  )
+
+  data$defra <- data$department %in% defra_orgs
+
+  return(data)
+
+}
+
+
+
+#' @title Apply skip logic
+#'
+#' @description Iteratively applies enforce_skip_logic to the necessary fields in the data.
+#'
+#' @param data data.frame
+#'
+#' @return cleaned data.frame
+#'
+#' @export
+
+w4_enforce_streaming <- function(data) {
+
+  conditions <- list(data$workplace %in% c("Civil service, including devolved administations", "test"),
+                     data$department %in% c("Office for National Statistics", "test"),
+                     data$highest_qualification != "Any other qualification",
+                     data$code_freq != "Never",
+                     data$other_coding_experience != "No",
+                     data$prev_coding_experience != "No",
+                     data$heard_of_RAP != "No")
+
+  skipped_cols <- list(colnames(data)[which(colnames(data) == "CS_grade"):which(colnames(data) == "ONS_directorate")],
+                       colnames(data)[which(colnames(data) == "ONS_directorate")],
+                       colnames(data)[which(colnames(data) == "qual_1_subject"):which(colnames(data) == "qual_3_learn_code")],
+                       colnames(data)[which(colnames(data) == "prac_use_open_source"):which(colnames(data) == "misc_coding")],
+                       colnames(data)[which(colnames(data) == "coding_ability_change"):which(colnames(data) == "first_learned")],
+                       colnames(data)[which(colnames(data) == "first_learned")],
+                       colnames(data)[which(colnames(data) == "know_RAP_champ"):which(colnames(data) == "RAP_comments")])
+
+  for(i in 1:length(conditions)){
+    data <- w4_enforce_skip_logic(data, conditions[[i]], skipped_cols[[i]])
+  }
+
+  return(data)
+
+}
+
+
+#' @title Check skip logic
+#'
+#' @description Checks whether the skip logic was followed correctly. Backtracking while filling the survey can result in inconsistent response sets.
+#' This check returns row numbers where questions which should have been skipped contain anything other than NA.
+#'
+#' @param data data.frame
+#' @param condition logical vector. Example: data$row == "skip response"
+#' @param skipped_cols character. questions that should have been skipped if condition != TRUE
+#'
+#' @return list of rows failing the check
+#'
+#' @export
+
+w4_check_skip_logic <- function(data, condition, skipped_cols) {
+
+  condition_failed <- !condition & !is.na(data[skipped_cols])
+
+  row_failed <- as.logical(rowSums(condition_failed))
+
+
+  return(
+    which(row_failed)
+  )
+
+}
+
+#' @title enforce skip logic
+#'
+#' @description Replaces values in rows with NAs where check_skip_logic has identified backtracking.
+#'
+#' @param data data.frame
+#' @param condition logical vector. Example: data$row == "skip response"
+#' @param skipped_cols character. questions that should have been skipped if condition != TRUE
+#'
+#' @return data.frame with rows failing the check replaced with NAs
+#'
+#' @export
+
+w4_enforce_skip_logic <- function(data, condition, skipped_cols) {
+
+  row_index <- w4_check_skip_logic(data, condition, skipped_cols)
+
+  data[row_index, skipped_cols] <- NA
+
+  return(data)
+
+}
diff --git a/man/derive_language_status.Rd b/man/derive_language_status.Rd
index 8477a56..fc313d9 100644
--- a/man/derive_language_status.Rd
+++ b/man/derive_language_status.Rd
@@ -13,5 +13,5 @@ derive_language_status(data)
 data.frame
 }
 \description{
-Derve the status of each programmming language as "access" (access only), "knowledge" (knowledge only), "both" or "neither".
+Derive the status of each programmming language as "access" (access only), "knowledge" (knowledge only), "both" or "neither".
 }
diff --git a/man/ingest.Rd b/man/ingest.Rd
index 9be5435..b970a63 100644
--- a/man/ingest.Rd
+++ b/man/ingest.Rd
@@ -5,7 +5,7 @@
 \title{Ingest smartsurvey data}
 \usage{
 ingest(
-  survey = "1167489",
+  survey = "1376897",
   token = Sys.getenv("CARS_TOKEN"),
   secret = Sys.getenv("CARS_SECRET"),
   proxies = Sys.getenv("alt_proxy"),
diff --git a/man/w2_rename_cols.Rd b/man/w2_rename_cols.Rd
index 00f6611..571830d 100644
--- a/man/w2_rename_cols.Rd
+++ b/man/w2_rename_cols.Rd
@@ -2,12 +2,12 @@
 % Please edit documentation in R/wave_2_preprocessing.R
 \name{w2_rename_cols}
 \alias{w2_rename_cols}
-\title{Rename columns (wave 3)}
+\title{Rename columns (wave 2)}
 \usage{
 w2_rename_cols(data)
 }
 \arguments{
-\item{data}{CARS wave 3 (2021) survey data (data.frame).}
+\item{data}{CARS wave 2 (2020) survey data (data.frame).}
 }
 \value{
 data.frame
diff --git a/man/w4_check_skip_logic.Rd b/man/w4_check_skip_logic.Rd
new file mode 100644
index 0000000..002bab7
--- /dev/null
+++ b/man/w4_check_skip_logic.Rd
@@ -0,0 +1,22 @@
+% Generated by roxygen2: do not edit by hand
+% Please edit documentation in R/wave_4_preprocessing.R
+\name{w4_check_skip_logic}
+\alias{w4_check_skip_logic}
+\title{Check skip logic}
+\usage{
+w4_check_skip_logic(data, condition, skipped_cols)
+}
+\arguments{
+\item{data}{data.frame}
+
+\item{condition}{logical vector. Example: data$row == "skip response"}
+
+\item{skipped_cols}{character. questions that should have been skipped if condition != TRUE}
+}
+\value{
+list of rows failing the check
+}
+\description{
+Checks whether the skip logic was followed correctly. Backtracking while filling the survey can result in inconsistent response sets.
+This check returns row numbers where questions which should have been skipped contain anything other than NA.
+}
diff --git a/man/w4_clean_departments.Rd b/man/w4_clean_departments.Rd
new file mode 100644
index 0000000..f29fa47
--- /dev/null
+++ b/man/w4_clean_departments.Rd
@@ -0,0 +1,17 @@
+% Generated by roxygen2: do not edit by hand
+% Please edit documentation in R/wave_4_preprocessing.R
+\name{w4_clean_departments}
+\alias{w4_clean_departments}
+\title{Clean department data}
+\usage{
+w4_clean_departments(data)
+}
+\arguments{
+\item{data}{cleaned CARS dataset}
+}
+\value{
+CARS dataset
+}
+\description{
+add NHS to department list and merge departments where needed.
+}
diff --git a/man/w4_enforce_skip_logic.Rd b/man/w4_enforce_skip_logic.Rd
new file mode 100644
index 0000000..ba1943a
--- /dev/null
+++ b/man/w4_enforce_skip_logic.Rd
@@ -0,0 +1,21 @@
+% Generated by roxygen2: do not edit by hand
+% Please edit documentation in R/wave_4_preprocessing.R
+\name{w4_enforce_skip_logic}
+\alias{w4_enforce_skip_logic}
+\title{enforce skip logic}
+\usage{
+w4_enforce_skip_logic(data, condition, skipped_cols)
+}
+\arguments{
+\item{data}{data.frame}
+
+\item{condition}{logical vector. Example: data$row == "skip response"}
+
+\item{skipped_cols}{character. questions that should have been skipped if condition != TRUE}
+}
+\value{
+data.frame with rows failing the check replaced with NAs
+}
+\description{
+Replaces values in rows with NAs where check_skip_logic has identified backtracking.
+}
diff --git a/man/w4_enforce_streaming.Rd b/man/w4_enforce_streaming.Rd
new file mode 100644
index 0000000..170dac7
--- /dev/null
+++ b/man/w4_enforce_streaming.Rd
@@ -0,0 +1,17 @@
+% Generated by roxygen2: do not edit by hand
+% Please edit documentation in R/wave_4_preprocessing.R
+\name{w4_enforce_streaming}
+\alias{w4_enforce_streaming}
+\title{Apply skip logic}
+\usage{
+w4_enforce_streaming(data)
+}
+\arguments{
+\item{data}{data.frame}
+}
+\value{
+cleaned data.frame
+}
+\description{
+Iteratively applies enforce_skip_logic to the necessary fields in the data.
+}
diff --git a/man/w4_rename_cols.Rd b/man/w4_rename_cols.Rd
new file mode 100644
index 0000000..5cd74df
--- /dev/null
+++ b/man/w4_rename_cols.Rd
@@ -0,0 +1,17 @@
+% Generated by roxygen2: do not edit by hand
+% Please edit documentation in R/wave_4_preprocessing.R
+\name{w4_rename_cols}
+\alias{w4_rename_cols}
+\title{Rename columns}
+\usage{
+w4_rename_cols(data)
+}
+\arguments{
+\item{data}{tidy CARS dataset}
+}
+\value{
+data.frame
+}
+\description{
+Renames columns and removes unnecessary columns
+}