diff --git a/src/subscriptions/client.py b/src/subscriptions/client.py
index 59be217..cab5248 100644
--- a/src/subscriptions/client.py
+++ b/src/subscriptions/client.py
@@ -1,4 +1,5 @@
 import os
+from urllib.parse import parse_qsl, urlencode, urlsplit, urlunsplit
 
 import httpx
 
@@ -137,5 +138,20 @@ def get_subscription(subscription_handle: str) -> dict:
     return _call("GET", f"/v1/subscription/{subscription_handle}")
 
 
+def get_payment_info_url(sub_handle: str, accept_url: str, cancel_url: str) -> str:
+    sub = get_subscription(sub_handle)
+    url = sub["hosted_page_links"]["payment_info"]
+    parts = urlsplit(url)
+    query = dict(parse_qsl(parts.query))
+    query["accept_url"] = accept_url
+    query["cancel_url"] = cancel_url
+    new_query = urlencode(query)
+    # If URL has a fragment (hash-based routing), append params to fragment
+    if parts.fragment:
+        return f"{urlunsplit((parts.scheme, parts.netloc, parts.path, '', ''))}#{parts.fragment}?{new_query}"
+    else:
+        return urlunsplit(parts._replace(query=new_query))
+
+
 def get_plan(plan_handle: str) -> dict:
     return _call("GET", f"/v1/plan/{plan_handle}")
diff --git a/tests/subscriptions/test_client.py b/tests/subscriptions/test_client.py
index 347795a..e86d8c9 100644
--- a/tests/subscriptions/test_client.py
+++ b/tests/subscriptions/test_client.py
@@ -89,3 +89,45 @@ def test_http_error_raises_frisbii_error(fake_httpx):
     with pytest.raises(client.FrisbiiError) as exc:
         client.get_plan("plan_simple")
     assert exc.value.status_code == 500
+
+
+def test_get_payment_info_url_appends_query_params(fake_httpx):
+    fake_httpx["queue"].append(
+        fake_httpx["Response"](
+            200,
+            {
+                "handle": "abo-1-1",
+                "hosted_page_links": {
+                    "payment_info": "https://checkout.reepay.com/#/subscription/pay/en_GB/x/abo-1-1"
+                },
+            },
+        )
+    )
+    url = client.get_payment_info_url(
+        "abo-1-1",
+        "https://app/compte/abonnement?carte=succes",
+        "https://app/compte/abonnement?carte=annule",
+    )
+    assert url.startswith(
+        "https://checkout.reepay.com/#/subscription/pay/en_GB/x/abo-1-1"
+    )
+    assert "accept_url=https%3A%2F%2Fapp%2Fcompte%2Fabonnement%3Fcarte%3Dsucces" in url
+    assert "cancel_url=https%3A%2F%2Fapp%2Fcompte%2Fabonnement%3Fcarte%3Dannule" in url
+
+
+def test_get_payment_info_url_merges_existing_query_string(fake_httpx):
+    fake_httpx["queue"].append(
+        fake_httpx["Response"](
+            200,
+            {
+                "handle": "abo-1-2",
+                "hosted_page_links": {
+                    "payment_info": "https://checkout.reepay.com/pay/abo-1-2?locale=fr"
+                },
+            },
+        )
+    )
+    url = client.get_payment_info_url("abo-1-2", "https://app/ok", "https://app/ko")
+    assert "locale=fr" in url
+    assert "accept_url=https%3A%2F%2Fapp%2Fok" in url
+    assert "cancel_url=https%3A%2F%2Fapp%2Fko" in url