diff --git a/poetry.lock b/poetry.lock
index ead9d94489f9c3495b81e3e5aa46596c1bfdac8e..e2edd9205cc868baf0053fe4610b9af50a9bb48c 100644
--- a/poetry.lock
+++ b/poetry.lock
@@ -106,18 +106,24 @@ marker = "python_version >= \"3.6\" and python_version < \"4.0\""
 name = "black"
 optional = false
 python-versions = ">=3.6"
-version = "19.10b0"
+version = "20.8b1"
 
 [package.dependencies]
 appdirs = "*"
-attrs = ">=18.1.0"
-click = ">=6.5"
+click = ">=7.1.2"
+mypy-extensions = ">=0.4.3"
 pathspec = ">=0.6,<1"
-regex = "*"
-toml = ">=0.9.4"
+regex = ">=2020.1.8"
+toml = ">=0.10.1"
 typed-ast = ">=1.4.0"
+typing-extensions = ">=3.7.4"
+
+[package.dependencies.dataclasses]
+python = "<3.7"
+version = ">=0.6"
 
 [package.extras]
+colorama = ["colorama (>=0.4.3)"]
 d = ["aiohttp (>=3.3.2)", "aiohttp-cors"]
 
 [[package]]
@@ -186,6 +192,15 @@ optional = false
 python-versions = "*"
 version = "1.0.1"
 
+[[package]]
+category = "dev"
+description = "A backport of the dataclasses module for Python 3.6"
+marker = "python_version >= \"3.6\" and python_version < \"3.7\""
+name = "dataclasses"
+optional = false
+python-versions = ">=3.6, <3.7"
+version = "0.7"
+
 [[package]]
 category = "dev"
 description = "Distribution utilities"
@@ -346,6 +361,15 @@ optional = false
 python-versions = ">=3.5"
 version = "4.7.6"
 
+[[package]]
+category = "dev"
+description = "Experimental type system extensions for programs checked with the mypy typechecker."
+marker = "python_version >= \"3.6\" and python_version < \"4.0\""
+name = "mypy-extensions"
+optional = false
+python-versions = "*"
+version = "0.4.3"
+
 [[package]]
 category = "dev"
 description = "Node.js virtual environment builder"
@@ -742,7 +766,7 @@ docs = ["sphinx", "jaraco.packaging (>=3.2)", "rst.linker (>=1.9)"]
 testing = ["pathlib2", "unittest2", "jaraco.itertools", "func-timeout"]
 
 [metadata]
-content-hash = "fe9defd881ff1ab7da675e5679bf01b12f9c8fe354feea820bd13fe0e6f20958"
+content-hash = "5fb062da355b9170f5dc0772c2ae50d4231081e04849305a97ac4d003b05bfde"
 python-versions = "^3.5.3"
 
 [metadata.files]
@@ -794,8 +818,8 @@ base58 = [
     {file = "base58-1.0.3.tar.gz", hash = "sha256:9a793c599979c497800eb414c852b80866f28daaed5494703fc129592cc83e60"},
 ]
 black = [
-    {file = "black-19.10b0-py36-none-any.whl", hash = "sha256:1b30e59be925fafc1ee4565e5e08abef6b03fe455102883820fe5ee2e4734e0b"},
-    {file = "black-19.10b0.tar.gz", hash = "sha256:c2edb73a08e9e0e6f65a0e6af18b059b8b1cdd5bef997d7a0b181df93dc81539"},
+    {file = "black-20.8b1-py3-none-any.whl", hash = "sha256:70b62ef1527c950db59062cda342ea224d772abdf6adc58b86a45421bab20a6b"},
+    {file = "black-20.8b1.tar.gz", hash = "sha256:1c02557aa099101b9d21496f8a914e9ed2222ef70336404eeeac8edba836fbea"},
 ]
 cffi = [
     {file = "cffi-1.14.1-cp27-cp27m-macosx_10_9_x86_64.whl", hash = "sha256:66dd45eb9530e3dde8f7c009f84568bc7cac489b93d04ac86e3111fb46e470c2"},
@@ -883,6 +907,10 @@ coverage-badge = [
     {file = "coverage-badge-1.0.1.tar.gz", hash = "sha256:142fd121f3bd14956aff3c45bff6f8bc37bd74c6350626a950ebb6accb24276e"},
     {file = "coverage_badge-1.0.1-py2.py3-none-any.whl", hash = "sha256:3796de21b4e190d38beb8806956946fbdb02fe3a2a7452b460a9cff958009833"},
 ]
+dataclasses = [
+    {file = "dataclasses-0.7-py3-none-any.whl", hash = "sha256:3459118f7ede7c8bea0fe795bff7c6c2ce287d01dd226202f7c9ebc0610a7836"},
+    {file = "dataclasses-0.7.tar.gz", hash = "sha256:494a6dcae3b8bcf80848eea2ef64c0cc5cd307ffc263e17cdf42f3e5420808e6"},
+]
 distlib = [
     {file = "distlib-0.3.1-py2.py3-none-any.whl", hash = "sha256:8c09de2c67b3e7deef7184574fc060ab8a793e7adbb183d942c389c8b13c52fb"},
     {file = "distlib-0.3.1.zip", hash = "sha256:edf6116872c863e1aa9d5bb7cb5e05a022c519a4594dc703843343a9ddd9bff1"},
@@ -952,6 +980,10 @@ multidict = [
     {file = "multidict-4.7.6-cp38-cp38-win_amd64.whl", hash = "sha256:7388d2ef3c55a8ba80da62ecfafa06a1c097c18032a501ffd4cabbc52d7f2b19"},
     {file = "multidict-4.7.6.tar.gz", hash = "sha256:fbb77a75e529021e7c4a8d4e823d88ef4d23674a202be4f5addffc72cbb91430"},
 ]
+mypy-extensions = [
+    {file = "mypy_extensions-0.4.3-py2.py3-none-any.whl", hash = "sha256:090fedd75945a69ae91ce1303b5824f428daf5a028d2f6ab8a299250a846f15d"},
+    {file = "mypy_extensions-0.4.3.tar.gz", hash = "sha256:2d82818f5bb3e369420cb3c4060a7970edba416647068eb4c5343488a6c604a8"},
+]
 nodeenv = [
     {file = "nodeenv-1.4.0-py2.py3-none-any.whl", hash = "sha256:4b0b77afa3ba9b54f4b6396e60b0c83f59eaeb2d63dc3cc7a70f7f4af96c82bc"},
 ]
diff --git a/pyproject.toml b/pyproject.toml
index 1732fea0d6aa94275f2f53654ef4a3156c45fbd4..b4d1b4090762289fdafca27684015a347abb70f1 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -22,7 +22,7 @@ pendulum = "^2.1.2"
 PyNaCl = "^1.3"
 
 [tool.poetry.dev-dependencies]
-black = {version = "^19.10b0", python = "^3.6"}
+black = {version = "^20.8b1", python = "^3.6"}
 pre-commit = "^1.18"
 pytest = "^6.0"
 pytest-cov = "^2.7"
diff --git a/silkaj/tx.py b/silkaj/tx.py
index 14898d105a95b8b19da60112c31a03b5dace9382..bcc5f499b9ad78acf903a84073db7afa0484a0ce 100644
--- a/silkaj/tx.py
+++ b/silkaj/tx.py
@@ -140,7 +140,12 @@ async def send_transaction(
         == "yes"
     ):
         await handle_intermediaries_transactions(
-            key, issuer_pubkey, tx_amounts, recipients, comment, outputbackchange,
+            key,
+            issuer_pubkey,
+            tx_amounts,
+            recipients,
+            comment,
+            outputbackchange,
         )
     else:
         client = ClientInstance().client
@@ -232,10 +237,18 @@ async def transaction_confirmation(
     tx = list()
     # display account situation
     display_amount(
-        tx, "pubkey's balance before tx", pubkey_amount, ud_value, currency_symbol,
+        tx,
+        "pubkey's balance before tx",
+        pubkey_amount,
+        ud_value,
+        currency_symbol,
     )
     display_amount(
-        tx, "total transaction amount", total_tx_amount, ud_value, currency_symbol,
+        tx,
+        "total transaction amount",
+        total_tx_amount,
+        ud_value,
+        currency_symbol,
     )
     display_amount(
         tx,
@@ -280,7 +293,12 @@ async def get_list_input_for_transaction(pubkey, TXamount):
 
 
 async def handle_intermediaries_transactions(
-    key, issuers, tx_amounts, outputAddresses, Comment="", OutputbackChange=None,
+    key,
+    issuers,
+    tx_amounts,
+    outputAddresses,
+    Comment="",
+    OutputbackChange=None,
 ):
     client = ClientInstance().client
     while True:
diff --git a/tests/test_tx.py b/tests/test_tx.py
index 33d5b4d7f1c14c7546d77f057753b5a427fc1116..4c17cff5ff3a6c093d6aefb146c2ab47ed1d3387 100644
--- a/tests/test_tx.py
+++ b/tests/test_tx.py
@@ -41,7 +41,15 @@ async def test_transaction_amount(monkeypatch):
         ([141.89, 141.99], None, ["A", "B"], [14189, 14199]),
         # tests for --amount_UD
         (None, [1.1], ["A"], [round(1.1 * udvalue)]),
-        (None, [1.9], ["A", "B",], [round(1.9 * udvalue), round(1.9 * udvalue)]),
+        (
+            None,
+            [1.9],
+            [
+                "A",
+                "B",
+            ],
+            [round(1.9 * udvalue), round(1.9 * udvalue)],
+        ),
         (None, [1.0001], ["A"], [round(1.0001 * udvalue)]),
         (None, [9.9999], ["A"], [round(9.9999 * udvalue)]),
         (None, [1.9, 2.3], ["A", "B"], [round(1.9 * udvalue), round(2.3 * udvalue)]),
diff --git a/tests/test_unit_tx.py b/tests/test_unit_tx.py
index 2441e366acc2d0573e8ddd82699e782d01850a6a..d0b755cb870da486c27756fefb9452676073228f 100644
--- a/tests/test_unit_tx.py
+++ b/tests/test_unit_tx.py
@@ -218,7 +218,8 @@ def test_compute_amounts_errors(capsys):
         with pytest.raises(SystemExit) as pytest_exit:
             # read output to check error.
             compute_amounts(
-                trial[0], trial[1],
+                trial[0],
+                trial[1],
             )
             expected_error = "Error: amount {0} is too low.".format(trial[0][0])
             assert capsys.readouterr() == expected_error
@@ -241,7 +242,8 @@ def test_compute_amounts():
     assert compute_amounts([1.001], ud_value) == [314]
     assert compute_amounts([1.009], ud_value) == [317]
     # This case will not happen in real use, but this particular function will allow it.
-    assert compute_amounts([0.0099], 100,) == [1]
+
+    assert compute_amounts([0.0099], 100) == [1]
 
 
 # transaction_amount()
@@ -289,7 +291,9 @@ def test_compute_amounts():
         (
             None,
             [0.00002],
-            ["DBM6F5ChMJzpmkUdL5zD9UXKExmZGfQ1AgPDQy4MxSBw",],
+            [
+                "DBM6F5ChMJzpmkUdL5zD9UXKExmZGfQ1AgPDQy4MxSBw",
+            ],
             "Error: amount 0.00002 is too low.",
         ),
         (