diff --git a/Hledger/Data/Amount.hs b/Hledger/Data/Amount.hs
--- a/Hledger/Data/Amount.hs
+++ b/Hledger/Data/Amount.hs
@@ -81,6 +81,7 @@
   divideMixedAmount,
   isNegativeMixedAmount,
   isZeroMixedAmount,
+  isReallyZeroMixedAmount,
   isReallyZeroMixedAmountCost,
   -- ** rendering
   showMixedAmount,
diff --git a/Hledger/Data/Commodity.hs b/Hledger/Data/Commodity.hs
--- a/Hledger/Data/Commodity.hs
+++ b/Hledger/Data/Commodity.hs
@@ -18,7 +18,7 @@
 
 
 -- characters than can't be in a non-quoted commodity symbol
-nonsimplecommoditychars = "0123456789-.@;\n \"{}" :: String
+nonsimplecommoditychars = "0123456789-.@;\n \"{}=" :: String
 
 quoteCommoditySymbolIfNeeded s | any (`elem` nonsimplecommoditychars) s = "\"" ++ s ++ "\""
                                | otherwise = s
diff --git a/Hledger/Data/Journal.hs b/Hledger/Data/Journal.hs
--- a/Hledger/Data/Journal.hs
+++ b/Hledger/Data/Journal.hs
@@ -49,8 +49,10 @@
   tests_Hledger_Data_Journal,
 )
 where
+import Control.Monad
 import Data.List
 -- import Data.Map (findWithDefault)
+import Data.Maybe
 import Data.Ord
 import Data.Time.Calendar
 import Data.Time.LocalTime
@@ -352,12 +354,72 @@
 -- all transactions balance, canonicalise amount formats, close any open
 -- timelog entries and so on.
 journalFinalise :: ClockTime -> LocalTime -> FilePath -> String -> JournalContext -> Journal -> Either String Journal
-journalFinalise tclock tlocal path txt ctx j@Journal{files=fs} =
-    journalBalanceTransactions $
+journalFinalise tclock tlocal path txt ctx j@Journal{files=fs} = do
+  (journalBalanceTransactions $
     journalCanonicaliseAmounts $
     journalCloseTimeLogEntries tlocal
-    j{files=(path,txt):fs, filereadtime=tclock, jContext=ctx}
+    j{files=(path,txt):fs, filereadtime=tclock, jContext=ctx})
+  >>= journalCheckBalanceAssertions
 
+-- | Check any balance assertions in the journal and return an error
+-- message if any of them fail.
+journalCheckBalanceAssertions :: Journal -> Either String Journal
+journalCheckBalanceAssertions j = do
+  let postingsByAccount = groupBy (\p1 p2 -> paccount p1 == paccount p2) $
+                          sortBy (comparing paccount) $
+                          journalPostings j
+  forM_ postingsByAccount checkBalanceAssertionsForAccount
+  Right j
+
+-- Check any balance assertions in this sequence of postings to a single account.
+checkBalanceAssertionsForAccount :: [Posting] -> Either String ()
+checkBalanceAssertionsForAccount ps
+  | null errs = Right ()
+  | otherwise = Left $ head errs
+  where
+    errs = fst $
+           foldl' checkBalanceAssertion ([],nullmixedamt) $
+           splitAssertions $
+           sortBy (comparing postingDate) ps
+
+-- Given a starting balance, accumulated errors, and a non-null sequence of
+-- postings to a single account with a balance assertion in the last:
+-- check that the final balance matches the balance assertion.
+-- If it does, return the new balance, otherwise add an error to the
+-- error list. Intended to be called from a fold.
+checkBalanceAssertion :: ([String],MixedAmount) -> [Posting] -> ([String],MixedAmount)
+checkBalanceAssertion (errs,bal) ps
+  | null ps = (errs,bal)
+  | isNothing assertion = (errs,bal)
+  |
+    -- bal' /= assertedbal  -- MixedAmount's Eq instance currently gets confused by different precisions
+    not $ isReallyZeroMixedAmount (bal' - assertedbal)
+      = (errs++[err], bal')
+  | otherwise = (errs,bal')
+  where
+    p = last ps
+    assertion = pbalanceassertion p
+    Just assertedbal = assertion
+    bal' = sum $ [bal] ++ map pamount ps
+    err = printf "Balance assertion failed for account %s on %s\n%safter\n   %s\nexpected balance is %s, actual balance was %s."
+                 (paccount p)
+                 (show $ postingDate p)
+                 (maybe "" (("In\n"++).show) $ ptransaction p)
+                 (show p)
+                 (showMixedAmount assertedbal)
+                 (showMixedAmount bal')
+
+-- Given a sequence of postings to a single account, split it into
+-- sub-sequences consisting of ordinary postings followed by a single
+-- balance-asserting posting. Postings not followed by a balance
+-- assertion are discarded.
+splitAssertions :: [Posting] -> [[Posting]]
+splitAssertions ps
+  | null rest = [[]]
+  | otherwise = (ps'++[head rest]):splitAssertions (tail rest)
+  where
+    (ps',rest) = break (isJust . pbalanceassertion) ps
+    
 -- | Fill in any missing amounts and check that all journal transactions
 -- balance, or return an error message. This is done after parsing all
 -- amounts and working out the canonical commodities, since balancing
diff --git a/Hledger/Data/Posting.hs b/Hledger/Data/Posting.hs
--- a/Hledger/Data/Posting.hs
+++ b/Hledger/Data/Posting.hs
@@ -71,6 +71,7 @@
                 ,pcomment=""
                 ,ptype=RegularPosting
                 ,ptags=[]
+                ,pbalanceassertion=Nothing
                 ,ptransaction=Nothing
                 }
 posting = nullposting
diff --git a/Hledger/Data/Types.hs b/Hledger/Data/Types.hs
--- a/Hledger/Data/Types.hs
+++ b/Hledger/Data/Types.hs
@@ -84,14 +84,15 @@
       pcomment :: String, -- ^ this posting's non-tag comment lines, as a single non-indented string
       ptype :: PostingType,
       ptags :: [Tag],
-      ptransaction :: Maybe Transaction  -- ^ this posting's parent transaction (co-recursive types).
-                                         -- Tying this knot gets tedious, Maybe makes it easier/optional.
+      pbalanceassertion :: Maybe MixedAmount,  -- ^ optional: the expected balance in the account after this posting
+      ptransaction :: Maybe Transaction    -- ^ this posting's parent transaction (co-recursive types).
+                                           -- Tying this knot gets tedious, Maybe makes it easier/optional.
     }
 
 -- The equality test for postings ignores the parent transaction's
 -- identity, to avoid infinite loops.
 instance Eq Posting where
-    (==) (Posting a1 b1 c1 d1 e1 f1 g1 h1 _) (Posting a2 b2 c2 d2 e2 f2 g2 h2 _) =  a1==a2 && b1==b2 && c1==c2 && d1==d2 && e1==e2 && f1==f2 && g1==g2 && h1==h2
+    (==) (Posting a1 b1 c1 d1 e1 f1 g1 h1 i1 _) (Posting a2 b2 c2 d2 e2 f2 g2 h2 i2 _) =  a1==a2 && b1==b2 && c1==c2 && d1==d2 && e1==e2 && f1==f2 && g1==g2 && h1==h2 && i1==i2
 
 data Transaction = Transaction {
       tdate :: Day,
diff --git a/Hledger/Read/CsvReader.hs b/Hledger/Read/CsvReader.hs
--- a/Hledger/Read/CsvReader.hs
+++ b/Hledger/Read/CsvReader.hs
@@ -557,7 +557,7 @@
       ,"the default-currency is: "++fromMaybe "unspecified" mdefaultcurrency
       ,"the parse error is:      "++show err
       ,"you may need to "
-       ++"change your amount, currency or default-currency rules, "
+       ++"change your amount or currency rules, "
        ++"or "++maybe "add a" (const "change your") mskip++" skip rule"
       ]
     -- Using costOfMixedAmount here to allow complex costs like "10 GBP @@ 15 USD".
@@ -593,7 +593,7 @@
    mamount    = getEffectiveAssignment rules record "amount"
    mamountin  = getEffectiveAssignment rules record "amount-in"
    mamountout = getEffectiveAssignment rules record "amount-out"
-   render     = fmap (renderTemplate rules record)
+   render     = fmap (strip . renderTemplate rules record)
  in
   case (render mamount, render mamountin, render mamountout) of
     (Just "", Nothing, Nothing) -> error' $ "amount has no value\n"++showRecord record
diff --git a/Hledger/Read/JournalReader.hs b/Hledger/Read/JournalReader.hs
--- a/Hledger/Read/JournalReader.hs
+++ b/Hledger/Read/JournalReader.hs
@@ -52,7 +52,9 @@
 import Data.Time.LocalTime
 import Safe (headDef, lastDef)
 #ifdef TESTS
-import Test.Framework
+import Test.HUnit
+import Test.Framework.HUnitWrapper
+-- import Test.Framework
 import Text.Parsec.Error
 #endif
 import Text.ParserCombinators.Parsec hiding (parse)
@@ -508,7 +510,7 @@
   account <- modifiedaccountname
   let (ptype, account') = (accountNamePostingType account, unbracket account)
   amount <- spaceandamountormissing
-  _ <- balanceassertion
+  massertion <- balanceassertion
   _ <- fixedlotprice
   many spacenonewline
   ctx <- getState
@@ -517,7 +519,7 @@
   -- oh boy
   d  <- maybe (return Nothing) (either (fail.show) (return.Just)) (parseWithCtx ctx date `fmap` dateValueFromTags tags)
   d2 <- maybe (return Nothing) (either (fail.show) (return.Just)) (parseWithCtx ctx date `fmap` date2ValueFromTags tags)
-  return posting{pdate=d, pdate2=d2, pstatus=status, paccount=account', pamount=amount, pcomment=comment, ptype=ptype, ptags=tags}
+  return posting{pdate=d, pdate2=d2, pstatus=status, paccount=account', pamount=amount, pcomment=comment, ptype=ptype, ptags=tags, pbalanceassertion=massertion}
 
 #ifdef TESTS
 test_postingp = do
@@ -559,9 +561,11 @@
   -- ,"postingp parses balance assertions and fixed lot prices" ~: do
     assertBool (isRight $ parseWithCtx nullctx postingp "  a  1 \"DE123\" =$1 { =2.2 EUR} \n")
 
-    let parse = parseWithCtx nullctx postingp " a\n ;next-line comment\n"
-    assertRight parse
-    assertEqual "next-line comment\n" (let Right p = parse in pcomment p)
+    -- let parse = parseWithCtx nullctx postingp " a\n ;next-line comment\n"
+    -- assertRight parse
+    -- let Right p = parse
+    -- assertEqual "next-line comment\n" (pcomment p)
+    -- assertEqual (Just nullmixedamt) (pbalanceassertion p)
 #endif       
 
 -- | Parse an account name, then apply any parent account prefix and/or account aliases currently in effect.
@@ -706,14 +710,14 @@
             return $ UnitPrice a))
          <|> return NoPrice
 
-balanceassertion :: GenParser Char JournalContext (Maybe Amount)
+balanceassertion :: GenParser Char JournalContext (Maybe MixedAmount)
 balanceassertion =
     try (do
           many spacenonewline
           char '='
           many spacenonewline
           a <- amountp -- XXX should restrict to a simple amount
-          return $ Just a)
+          return $ Just $ Mixed [a])
          <|> return Nothing
 
 -- http://ledger-cli.org/3.0/doc/ledger3.html#Fixing-Lot-Prices
diff --git a/Hledger/Reports.hs b/Hledger/Reports.hs
--- a/Hledger/Reports.hs
+++ b/Hledger/Reports.hs
@@ -34,7 +34,8 @@
   TransactionsReport,
   TransactionsReportItem,
   triDate,
-  triBalance,
+  triSimpleBalance,
+  transactionsReportByCommodity,
   journalTransactionsReport,
   accountTransactionsReport,
   -- * Accounts report
@@ -435,8 +436,38 @@
                               )
 
 triDate (t,_,_,_,_,_) = tdate t
-triBalance (_,_,_,_,_,Mixed a) = case a of [] -> "0"
-                                           (Amount{aquantity=q}):_ -> show q
+triAmount (_,_,_,_,a,_) = a
+triSimpleBalance (_,_,_,_,_,Mixed a) = case a of [] -> "0"
+                                                 (Amount{aquantity=q}):_ -> show q
+
+-- Split a transactions report whose items may involve several commodities,
+-- into one or more single-commodity transactions reports.
+transactionsReportByCommodity :: TransactionsReport -> [TransactionsReport]
+transactionsReportByCommodity tr =
+  [filterTransactionsReportByCommodity c tr | c <- transactionsReportCommodities tr]
+  where
+    transactionsReportCommodities (_,items) =
+      nub $ sort $ map acommodity $ concatMap (amounts . triAmount) items
+
+-- Remove transaction report items and item amount components that
+-- don't involve the specified commodity. Other item fields like the
+-- running balance and the transaction are left unchanged.
+filterTransactionsReportByCommodity :: Commodity -> TransactionsReport -> TransactionsReport
+filterTransactionsReportByCommodity c (label,items) =
+  (label, fixTransactionsReportItemBalances $ concat [filterTransactionsReportItemByCommodity c i | i <- items])
+  where
+    filterTransactionsReportItemByCommodity c (t,t2,s,o,Mixed as,bal)
+      | c `elem` cs = [item']
+      | otherwise   = []
+      where
+        cs = map acommodity as
+        item' = (t,t2,s,o,Mixed as',bal)
+        as' = filter ((==c).acommodity) as
+    fixTransactionsReportItemBalances is = reverse $ go nullmixedamt $ reverse is
+      where
+        go _ [] = []
+        go bal ((t,t2,s,o,amt,_):is) = (t,t2,s,o,amt,bal'):go bal' is
+          where bal' = bal + amt
 
 -- | Select transactions from the whole journal for a transactions report,
 -- with no \"current\" account. The end result is similar to
diff --git a/hledger-lib.cabal b/hledger-lib.cabal
--- a/hledger-lib.cabal
+++ b/hledger-lib.cabal
@@ -1,5 +1,5 @@
 name:           hledger-lib
-version: 0.20.0.1
+version: 0.21
 category:       Finance
 synopsis:       Core data types, parsers and utilities for the hledger accounting tool.
 description:
@@ -18,12 +18,12 @@
 bug-reports:    http://hledger.org/bugs
 stability:      beta
 tested-with:    GHC==7.2.2, GHC==7.4.2, GHC==7.6.1
-cabal-version:  >= 1.8
+cabal-version:  >= 1.10
 build-type:     Simple
 -- data-dir:       data
 -- data-files:
 -- extra-tmp-files:
--- extra-source-files:
+extra-source-files: tests/suite.hs
 --   README
 --   sample.ledger
 --   sample.timelog
@@ -75,10 +75,38 @@
                  ,transformers >= 0.2 && < 0.4
                  ,utf8-string >= 0.3.5 && < 0.4
                  ,HUnit
+  default-language: Haskell2010
 
 source-repository head
   type:     git
   location: https://github.com/simonmichael/hledger
+
+test-suite tests
+  type:     exitcode-stdio-1.0
+  main-is:  tests/suite.hs
+  ghc-options: -Wall
+  build-depends: hledger-lib
+               , base >= 4.3 && < 5
+               , cmdargs
+               , containers
+               , csv
+               , directory
+               , filepath
+               , HUnit
+               , mtl
+               , old-locale
+               , old-time
+               , parsec
+               , pretty-show
+               , regex-compat
+               , regexpr
+               , safe
+               , split
+               , test-framework
+               , test-framework-hunit
+               , time
+               , transformers
+  default-language: Haskell2010
 
 -- cf http://www.haskell.org/cabal/release/cabal-latest/doc/users-guide/authors.html
 
diff --git a/tests/suite.hs b/tests/suite.hs
new file mode 100644
--- /dev/null
+++ b/tests/suite.hs
@@ -0,0 +1,6 @@
+import Hledger (tests_Hledger)
+import Test.Framework.Providers.HUnit (hUnitTestToTests)
+import Test.Framework.Runners.Console (defaultMain)
+
+main :: IO ()
+main = defaultMain $ hUnitTestToTests tests_Hledger