diff --git a/hledger/Hledger/Cli/Commands/Accounts.hs b/hledger/Hledger/Cli/Commands/Accounts.hs
index 99567458f..ad0598aa1 100644
--- a/hledger/Hledger/Cli/Commands/Accounts.hs
+++ b/hledger/Hledger/Cli/Commands/Accounts.hs
@@ -28,6 +28,8 @@ import System.Console.CmdArgs.Explicit as C
 import Hledger
 import Hledger.Cli.CliOptions
 import Control.Monad (forM_)
+import Data.Maybe (fromMaybe)
+import Safe (headDef)
 
 
 -- | Command line options for this command.
@@ -35,11 +37,13 @@ accountsmode = hledgerCommandMode
   $(embedFileRelative "Hledger/Cli/Commands/Accounts.txt")
   (flattreeflags False ++
   [flagReq  ["drop"] (\s opts -> Right $ setopt "drop" s opts) "N" "flat mode: omit N leading account name parts"
+  ,flagNone ["used"] (setboolopt "used") "show only accounts used by transactions"
   ,flagNone ["declared"] (setboolopt "declared") "show only accounts declared by account directive"
-  ,flagNone ["used"] (setboolopt "used") "show only accounts referenced by transactions"
-  ,flagNone ["types"] (setboolopt "types") "show accounts' types, when known"
-  ,flagNone ["positions"] (setboolopt "positions") "show where accounts were declared"
-  ,flagNone ["directives"] (setboolopt "directives") "show valid account directives usable in journals"
+  ,flagNone ["undeclared"] (setboolopt "undeclared") "show accounts used but not declared"
+  ,flagNone ["find"] (setboolopt "find") "find the first account matched by the first command argument (a case-insensitive infix regexp or account name)"
+  ,flagNone ["types"] (setboolopt "types") "also show account types when known"
+  ,flagNone ["positions"] (setboolopt "positions") "also show where accounts were declared"
+  ,flagNone ["directives"] (setboolopt "directives") "show as account directives, for use in journals"
   ])
   [generalflagsgroup1]
   hiddenflags
@@ -51,8 +55,10 @@ accounts CliOpts{rawopts_=rawopts, reportspec_=ReportSpec{_rsQuery=query,_rsRepo
 
   -- 1. identify the accounts we'll show
   let tree     = tree_ ropts
-      decl = boolopt "declared" rawopts
       used = boolopt "used"     rawopts
+      decl = boolopt "declared" rawopts
+      undecl = boolopt "undeclared" rawopts
+      find_ = boolopt "find" rawopts
       types = boolopt "types"    rawopts
       positions = boolopt "positions" rawopts
       directives = boolopt "directives" rawopts
@@ -63,13 +69,29 @@ accounts CliOpts{rawopts_=rawopts, reportspec_=ReportSpec{_rsQuery=query,_rsRepo
       dep = dbg4 "depth" $ queryDepth $ filterQuery queryIsDepth query
       matcheddeclaredaccts =
         dbg4 "matcheddeclaredaccts" $
+        nub $
         filter (matchesAccountExtra (journalAccountType j) (journalInheritedAccountTags j) nodepthq)
           $ map fst $ jdeclaredaccounts j
-      matchedusedaccts = dbg5 "matchedusedaccts" $ map paccount $ journalPostings $ filterJournalPostings nodepthq j
-      accts = dbg5 "accts to show" $
-        if | decl     && not used -> matcheddeclaredaccts
-           | not decl && used     -> matchedusedaccts
-           | otherwise            -> matcheddeclaredaccts ++ matchedusedaccts
+      matchedusedaccts = dbg5 "matchedusedaccts" $ nub $ map paccount $ journalPostings $ filterJournalPostings nodepthq j
+      matchedundeclaredaccts = dbg5 "matchedundeclaredaccts" $ nub $ matchedusedaccts \\ matcheddeclaredaccts
+      -- keep synced with aregister
+      matchedacct = dbg5 "matchedacct" $
+        fromMaybe (error' $ show apat ++ " did not match any account.")   -- PARTIAL:
+            . firstMatch $ journalAccountNamesDeclaredOrImplied j
+        where
+          firstMatch = case toRegexCI $ T.pack apat of
+              Right re -> find (regexMatchText re)
+              Left  _  -> const Nothing
+          apat = headDef
+            (error' "With --find, please provide an account name or\naccount pattern (case-insensitive, infix, regexp) as first command argument.")
+            $ listofstringopt "args" rawopts
+
+      accts = dbg5 "accts to show" $ if
+        | find_                -> [matchedacct]
+        | undecl               -> matchedundeclaredaccts
+        | decl     && not used -> matcheddeclaredaccts
+        | not decl && used     -> matchedusedaccts
+        | otherwise            -> matcheddeclaredaccts ++ matchedusedaccts
 
   -- 2. sort them by declaration order (then undeclared accounts alphabetically)
   -- within each group of siblings
diff --git a/hledger/Hledger/Cli/Commands/Accounts.md b/hledger/Hledger/Cli/Commands/Accounts.md
index ecc241311..9a9712357 100644
--- a/hledger/Hledger/Cli/Commands/Accounts.md
+++ b/hledger/Hledger/Cli/Commands/Accounts.md
@@ -3,10 +3,16 @@ Show account names.
 
 _FLAGS
 
-This command lists account names, either declared with account directives
-(--declared), posted to (--used), or both (the default).
-With query arguments, only matched account names and account names 
-referenced by matched postings are shown.
+This command lists account names.
+By default it shows all known accounts, either used in transactions or declared with account directives.
+
+With query arguments, only matched account names and account names referenced by matched postings are shown.
+
+Or it can show just
+the used accounts (`--used`),
+the declared accounts (`--declared`),
+the accounts used but not declared (`--undeclared`),
+or the first account matched by an account name pattern, if any (`--find`).
 
 It shows a flat list by default. With `--tree`, it uses indentation to
 show the account hierarchy.
@@ -22,6 +28,12 @@ these may be useful when troubleshooting account display order.
 
 With `--directives`, it adds the `account` keyword, showing
 valid account directives which can be pasted into a journal file.
+This is useful together with `--undeclared` to update your account declarations
+when `check accounts` reports undeclared accounts. 
+
+The `--find` flag can be used to look up a single account name, in the same way
+that the `aregister` command does. It returns the alphanumerically-first matched
+account name, or if none can be found, it fails with a non-zero exit code.
 
 Examples:
 
@@ -36,3 +48,7 @@ income:gifts
 income:salary
 liabilities:debts
 ```
+```shell
+$ hledger accounts --undeclared --directives >> $LEDGER_FILE
+$ hledger check accounts
+```
diff --git a/hledger/Hledger/Cli/Commands/Aregister.hs b/hledger/Hledger/Cli/Commands/Aregister.hs
index ae85ccb15..f27057ad1 100644
--- a/hledger/Hledger/Cli/Commands/Aregister.hs
+++ b/hledger/Hledger/Cli/Commands/Aregister.hs
@@ -75,6 +75,7 @@ aregister opts@CliOpts{rawopts_=rawopts,reportspec_=rspec} j = do
       []     -> error' $ help <> ".\nPlease provide an account name or a (case-insensitive, infix, regexp) pattern."
       (a:as) -> return (a, map T.pack as)
   let
+    -- keep synced with accounts --find
     acct = fromMaybe (error' $ help <> ",\nbut " ++ show apat++" did not match any account.")   -- PARTIAL:
            . firstMatch $ journalAccountNamesDeclaredOrImplied j
     firstMatch = case toRegexCI $ T.pack apat of