diff --git a/NEWS.md b/NEWS.md
index bfdda9550..1c9450d90 100644
--- a/NEWS.md
+++ b/NEWS.md
@@ -2,6 +2,7 @@
 
 ## Documentation
 
+- The documentation of the `rt` argument has been expanded in the case where `rt = NULL` to make explicit the settings that are applied in that case. By @jamesmbaazam in #779 and reviewed by @sbfnk.
 - The README has been updated to link to the free course on nowcasting and forecasting. The availability of variational inference, Laplace approximation, and Pathfinder through `cmdstanr` has also be surfaced. By @jamesmbaazam in #753 and reviewed by @seabbs.
 - Some implicit argument defaults have been made explicit in the function definition. By @Bisaloo in #729.
 - The installation guide in the README has been updated to provide instructions for configuring the C toolchain of Windows, MacOS, and Linux. By @jamesmbaazam in #707 and reviewed by @sbfnk.
diff --git a/R/create.R b/R/create.R
index 154b28b86..6e0cf94e1 100644
--- a/R/create.R
+++ b/R/create.R
@@ -239,8 +239,10 @@ create_future_rt <- function(future = c("latest", "project", "estimate"),
 #' Takes the output from [rt_opts()] and converts it into a list understood by
 #' stan.
 #' @param rt A list of options as generated by [rt_opts()] defining Rt
-#' estimation. Defaults to [rt_opts()]. Set to `NULL` to switch to using back
-#' calculation rather than generating infections using Rt.
+#' estimation. Defaults to [rt_opts()]. To generate new infections using
+#' the non-mechanistic model instead of the renewal equation model, use
+#' `rt = NULL`. The non-mechanistic model internally uses the setting
+#' `rt = rt_opts(use_rt = FALSE, future = "project", gp_on = "R0")`.
 #'
 #' @param breakpoints An integer vector (binary) indicating the location of
 #' breakpoints.
diff --git a/man/create_rt_data.Rd b/man/create_rt_data.Rd
index 3c5233795..8349db1cf 100644
--- a/man/create_rt_data.Rd
+++ b/man/create_rt_data.Rd
@@ -8,8 +8,10 @@ create_rt_data(rt = rt_opts(), breakpoints = NULL, delay = 0, horizon = 0)
 }
 \arguments{
 \item{rt}{A list of options as generated by \code{\link[=rt_opts]{rt_opts()}} defining Rt
-estimation. Defaults to \code{\link[=rt_opts]{rt_opts()}}. Set to \code{NULL} to switch to using back
-calculation rather than generating infections using Rt.}
+estimation. Defaults to \code{\link[=rt_opts]{rt_opts()}}. To generate new infections using
+the non-mechanistic model instead of the renewal equation model, use
+\code{rt = NULL}. The non-mechanistic model internally uses the setting
+\code{rt = rt_opts(use_rt = FALSE, future = "project", gp_on = "R0")}.}
 
 \item{breakpoints}{An integer vector (binary) indicating the location of
 breakpoints.}
diff --git a/man/create_stan_data.Rd b/man/create_stan_data.Rd
index e755fca8d..ed80f379e 100644
--- a/man/create_stan_data.Rd
+++ b/man/create_stan_data.Rd
@@ -23,8 +23,10 @@ create_stan_data(
 \code{\link[=get_seeding_time]{get_seeding_time()}}.}
 
 \item{rt}{A list of options as generated by \code{\link[=rt_opts]{rt_opts()}} defining Rt
-estimation. Defaults to \code{\link[=rt_opts]{rt_opts()}}. Set to \code{NULL} to switch to using back
-calculation rather than generating infections using Rt.}
+estimation. Defaults to \code{\link[=rt_opts]{rt_opts()}}. To generate new infections using
+the non-mechanistic model instead of the renewal equation model, use
+\code{rt = NULL}. The non-mechanistic model internally uses the setting
+\code{rt = rt_opts(use_rt = FALSE, future = "project", gp_on = "R0")}.}
 
 \item{gp}{A list of options as generated by \code{\link[=gp_opts]{gp_opts()}} to define the
 Gaussian process. Defaults to \code{\link[=gp_opts]{gp_opts()}}. Set to \code{NULL} to disable the
diff --git a/man/epinow.Rd b/man/epinow.Rd
index fd9b70b3c..6046dea56 100644
--- a/man/epinow.Rd
+++ b/man/epinow.Rd
@@ -49,8 +49,10 @@ used as the \code{truncation} argument here, thereby propagating the uncertainty
 in the estimate.}
 
 \item{rt}{A list of options as generated by \code{\link[=rt_opts]{rt_opts()}} defining Rt
-estimation. Defaults to \code{\link[=rt_opts]{rt_opts()}}. Set to \code{NULL} to switch to using back
-calculation rather than generating infections using Rt.}
+estimation. Defaults to \code{\link[=rt_opts]{rt_opts()}}. To generate new infections using
+the non-mechanistic model instead of the renewal equation model, use
+\code{rt = NULL}. The non-mechanistic model internally uses the setting
+\code{rt = rt_opts(use_rt = FALSE, future = "project", gp_on = "R0")}.}
 
 \item{backcalc}{A list of options as generated by \code{\link[=backcalc_opts]{backcalc_opts()}} to
 define the back calculation. Defaults to \code{\link[=backcalc_opts]{backcalc_opts()}}.}
diff --git a/man/estimate_infections.Rd b/man/estimate_infections.Rd
index f77981a07..cab919f85 100644
--- a/man/estimate_infections.Rd
+++ b/man/estimate_infections.Rd
@@ -45,8 +45,10 @@ used as the \code{truncation} argument here, thereby propagating the uncertainty
 in the estimate.}
 
 \item{rt}{A list of options as generated by \code{\link[=rt_opts]{rt_opts()}} defining Rt
-estimation. Defaults to \code{\link[=rt_opts]{rt_opts()}}. Set to \code{NULL} to switch to using back
-calculation rather than generating infections using Rt.}
+estimation. Defaults to \code{\link[=rt_opts]{rt_opts()}}. To generate new infections using
+the non-mechanistic model instead of the renewal equation model, use
+\code{rt = NULL}. The non-mechanistic model internally uses the setting
+\code{rt = rt_opts(use_rt = FALSE, future = "project", gp_on = "R0")}.}
 
 \item{backcalc}{A list of options as generated by \code{\link[=backcalc_opts]{backcalc_opts()}} to
 define the back calculation. Defaults to \code{\link[=backcalc_opts]{backcalc_opts()}}.}
diff --git a/man/get_seeding_time.Rd b/man/get_seeding_time.Rd
index e240824fa..9be232e89 100644
--- a/man/get_seeding_time.Rd
+++ b/man/get_seeding_time.Rd
@@ -16,8 +16,10 @@ details.}
 For backwards compatibility a list of summary parameters can also be passed.}
 
 \item{rt}{A list of options as generated by \code{\link[=rt_opts]{rt_opts()}} defining Rt
-estimation. Defaults to \code{\link[=rt_opts]{rt_opts()}}. Set to \code{NULL} to switch to using back
-calculation rather than generating infections using Rt.}
+estimation. Defaults to \code{\link[=rt_opts]{rt_opts()}}. To generate new infections using
+the non-mechanistic model instead of the renewal equation model, use
+\code{rt = NULL}. The non-mechanistic model internally uses the setting
+\code{rt = rt_opts(use_rt = FALSE, future = "project", gp_on = "R0")}.}
 }
 \value{
 An integer seeding time
diff --git a/man/regional_epinow.Rd b/man/regional_epinow.Rd
index 64b150922..67ab215c5 100644
--- a/man/regional_epinow.Rd
+++ b/man/regional_epinow.Rd
@@ -48,8 +48,10 @@ used as the \code{truncation} argument here, thereby propagating the uncertainty
 in the estimate.}
 
 \item{rt}{A list of options as generated by \code{\link[=rt_opts]{rt_opts()}} defining Rt
-estimation. Defaults to \code{\link[=rt_opts]{rt_opts()}}. Set to \code{NULL} to switch to using back
-calculation rather than generating infections using Rt.}
+estimation. Defaults to \code{\link[=rt_opts]{rt_opts()}}. To generate new infections using
+the non-mechanistic model instead of the renewal equation model, use
+\code{rt = NULL}. The non-mechanistic model internally uses the setting
+\code{rt = rt_opts(use_rt = FALSE, future = "project", gp_on = "R0")}.}
 
 \item{backcalc}{A list of options as generated by \code{\link[=backcalc_opts]{backcalc_opts()}} to
 define the back calculation. Defaults to \code{\link[=backcalc_opts]{backcalc_opts()}}.}
diff --git a/man/run_region.Rd b/man/run_region.Rd
index 802b7b8f3..078a301d6 100644
--- a/man/run_region.Rd
+++ b/man/run_region.Rd
@@ -46,8 +46,10 @@ used as the \code{truncation} argument here, thereby propagating the uncertainty
 in the estimate.}
 
 \item{rt}{A list of options as generated by \code{\link[=rt_opts]{rt_opts()}} defining Rt
-estimation. Defaults to \code{\link[=rt_opts]{rt_opts()}}. Set to \code{NULL} to switch to using back
-calculation rather than generating infections using Rt.}
+estimation. Defaults to \code{\link[=rt_opts]{rt_opts()}}. To generate new infections using
+the non-mechanistic model instead of the renewal equation model, use
+\code{rt = NULL}. The non-mechanistic model internally uses the setting
+\code{rt = rt_opts(use_rt = FALSE, future = "project", gp_on = "R0")}.}
 
 \item{backcalc}{A list of options as generated by \code{\link[=backcalc_opts]{backcalc_opts()}} to
 define the back calculation. Defaults to \code{\link[=backcalc_opts]{backcalc_opts()}}.}