diff --git a/src/amount.ml b/src/amount.ml
index 3caeaf68..7ff74514 100644
--- a/src/amount.ml
+++ b/src/amount.ml
@@ -1,8 +1,4 @@
-(* TODO
-   have a currency agnostic amount_lib.ml
-   and specialize amount.ml to Config.currency??
-
-   have safe amount arithmetic *)
+(* TODO implement operations on amounts *)
 open Syntax
 
 type sign =
diff --git a/src/api.ml b/src/api.ml
index 062ca181..2a6ea9cc 100644
--- a/src/api.ml
+++ b/src/api.ml
@@ -85,9 +85,6 @@ module Bytes64 = struct
       ~decode:of_octets Caqti_type.octets
 end
 
-(* TODO error response
-   - use GANA error codes
-     https://git.gnunet.org/gana.git/tree/gnu-taler-error-codes/registry.rec *)
 module ErrorDetail = struct
   type t = {
     code: int;
diff --git a/src/headers.ml b/src/headers.ml
index fd6ebfc7..6d4a64f7 100644
--- a/src/headers.ml
+++ b/src/headers.ml
@@ -6,7 +6,8 @@ let accept_header_value =
 let avail_languages_header_value =
   Fmt.str "%a" (Fmt.array ~sep:(Fmt.any ", ") Fmt.string) Assets.Language.arr
 
-(* TODO Cohttp raises on invalid *)
+(* TODO better headers_lib
+   Cohttp raises on invalid *)
 let select_mimetype headers =
   let opt = Vif.Headers.get headers "accept" in
   Cohttp.Accept.media_ranges opt
diff --git a/src/keys.ml b/src/keys.ml
index 6ad2a4f6..382079a9 100644
--- a/src/keys.ml
+++ b/src/keys.ml
@@ -1,7 +1,6 @@
 open Syntax
 open Crypto
 
-(* TODO better error type *)
 type 'a result = ('a, string) Result.t
 
 module type S = sig
@@ -33,8 +32,8 @@ module Make (Conn : Pg.CONN) : S = struct
 
   let conn = (module Conn : Pg.CONN)
 
-  (* TODO
-     error "key not found", either:
+  (* TODO better error
+     can only be "key not found", either:
        - we tried to sign with a key that is not ours
        - key was revoked
        - bad keyring state *)
diff --git a/src/pg.ml b/src/pg.ml
index eb4c789e..b4543f8a 100644
--- a/src/pg.ml
+++ b/src/pg.ml
@@ -1,11 +1,6 @@
 (* TODO
-   can we avoid amount tuple boilerplate?
-   clean up caqti error type
-
    transaction
-
-   GNU Taler use of db-events?
-   it seems caqti/pgx does not support it *)
+   GNU Taler use of db-events? it seems caqti/pgx does not support it *)
 
 module type CONN = Caqti_miou.CONNECTION
 
diff --git a/src/respond.ml b/src/respond.ml
index 17f67039..a7780c36 100644
--- a/src/respond.ml
+++ b/src/respond.ml
@@ -1,6 +1,3 @@
-(* TODO response
-   use ErrorDetail *)
-
 let encode_error_detail err =
   match Api.(encode ErrorDetail.jsont err) with
   | Error e -> Fmt.failwith "json encoding error on `ErrorDetail`: %s." e
diff --git a/src/secmod_eddsa.ml b/src/secmod_eddsa.ml
index 6cf9ac1e..2eece202 100644
--- a/src/secmod_eddsa.ml
+++ b/src/secmod_eddsa.ml
@@ -103,7 +103,7 @@ let split_in_periodes ~start ~end_ =
   in
   go acc start end_
 
-(* TODO do not exceed lookahead (probably more important...) *)
+(* TODO do not exceed lookahead *)
 (* try to not generate keys with validity start in the past *)
 let gen_additional_keys_until_lookahead ~now l =
   let start =
@@ -118,7 +118,6 @@ let gen_additional_keys_until_lookahead ~now l =
     let new_keys = List.map (fun (t1, t2) -> gen_key t1 t2) periodes in
     new_keys
 
-(* TODO config *)
 let sm_key_fpath =
   Result.get_ok
   @@
@@ -221,5 +220,5 @@ end
   - more checks
   - sign: check timestamps before signing
   - schedule tasks
-  - !lock
+  - ! use lock
 *)
diff --git a/src/syntax.ml b/src/syntax.ml
index 7db544ca..aafcfbcf 100644
--- a/src/syntax.ml
+++ b/src/syntax.ml
@@ -1,7 +1,10 @@
 let ( let* ) o f = match o with Ok v -> f v | Error _ as e -> e
 let ( let+ ) o f = match o with Ok v -> Ok (f v) | Error _ as e -> e
 
-(* TODO use polymorphic variant for errors *)
+(* TODO better errors
+   use polymorphic variant for errors
+   use GANA error codes:
+     https://git.gnunet.org/gana.git/tree/gnu-taler-error-codes/registry.rec *)
 let unwrap_err_msg o = match o with Error (`Msg e) -> Error e | Ok v -> Ok v
 
 let unwrap_err_caqti o =
diff --git a/src/time.mli b/src/time.mli
index ca3322c4..7955f822 100644
--- a/src/time.mli
+++ b/src/time.mli
@@ -50,7 +50,6 @@ module Timestamp : sig
   val of_absolute : TimeAbsolute.t -> t
   val of_ptime : Ptime.t -> t
 
-  (* TODO add pp *)
   (* - *)
   val bin : t Bin.t
   val caqti : t Caqti_type.t