diff --git a/packages/merchant-backoffice-ui/src/paths/instance/templates/qr/QrPage.tsx b/packages/merchant-backoffice-ui/src/paths/instance/templates/qr/QrPage.tsx
index 90084f113..0f30efafd 100644
--- a/packages/merchant-backoffice-ui/src/paths/instance/templates/qr/QrPage.tsx
+++ b/packages/merchant-backoffice-ui/src/paths/instance/templates/qr/QrPage.tsx
@@ -34,6 +34,7 @@ import { useBackendContext } from "../../../../context/backend.js";
 import { useConfigContext } from "../../../../context/config.js";
 import { useInstanceContext } from "../../../../context/instance.js";
 import { MerchantBackend } from "../../../../declaration.js";
+import { stringifyPayTemplateUri } from "@gnu-taler/taler-util";
 
 type Entity = MerchantBackend.Template.UsingTemplateDetails;
 
@@ -64,46 +65,47 @@ export function QrPage({ template, id: templateId, onBack }: Props): VNode {
   const fixedAmount = !!template.template_contract.amount;
   const fixedSummary = !!template.template_contract.summary;
 
-  const params = new URLSearchParams();
+  const templateParams: Record<string, string> = {}
   if (!fixedAmount) {
     if (state.amount) {
-      params.append("amount", state.amount);
+      templateParams.amount = state.amount
     } else {
-      params.append("amount", config.currency);
+      templateParams.amount = config.currency
     }
   }
+
   if (!fixedSummary) {
-    params.append("summary", state.summary ?? "");
+    templateParams.summary = state.summary ?? ""
   }
 
-  const paramsStr = fixedAmount && fixedSummary ? "" : "?" + params.toString();
-  const merchantURL = new URL(backendUrl);
+  const merchantBaseUrl = new URL(backendUrl).href;
 
-  const talerProto =
-    merchantURL.protocol === "http:" ? "taler+http:" : "taler:";
-
-  const payTemplateUri = `${talerProto}//pay-template/${merchantURL.hostname}/${templateId}${paramsStr}`;
+  const payTemplateUri = stringifyPayTemplateUri({
+    merchantBaseUrl,
+    templateId,
+    templateParams
+  })
 
   const issuer = encodeURIComponent(
-    `${new URL(backendUrl).hostname}/${instanceId}`,
+    `${new URL(backendUrl).host}/${instanceId}`,
   );
   const oauthUri = !template.pos_algorithm
     ? undefined
     : template.pos_algorithm === 1
-    ? `otpauth://totp/${issuer}:${templateId}?secret=${template.pos_key}&issuer=${issuer}&algorithm=SHA1&digits=8&period=30`
-    : template.pos_algorithm === 2
-    ? `otpauth://totp/${issuer}:${templateId}?secret=${template.pos_key}&issuer=${issuer}&algorithm=SHA1&digits=8&period=30`
-    : undefined;
+      ? `otpauth://totp/${issuer}:${templateId}?secret=${template.pos_key}&issuer=${issuer}&algorithm=SHA1&digits=8&period=30`
+      : template.pos_algorithm === 2
+        ? `otpauth://totp/${issuer}:${templateId}?secret=${template.pos_key}&issuer=${issuer}&algorithm=SHA1&digits=8&period=30`
+        : undefined;
 
   const keySlice = template.pos_key?.substring(0, 4);
 
   const oauthUriWithoutSecret = !template.pos_algorithm
     ? undefined
     : template.pos_algorithm === 1
-    ? `otpauth://totp/${issuer}:${templateId}?secret=${keySlice}...&issuer=${issuer}&algorithm=SHA1&digits=8&period=30`
-    : template.pos_algorithm === 2
-    ? `otpauth://totp/${issuer}:${templateId}?secret=${keySlice}...&issuer=${issuer}&algorithm=SHA1&digits=8&period=30`
-    : undefined;
+      ? `otpauth://totp/${issuer}:${templateId}?secret=${keySlice}...&issuer=${issuer}&algorithm=SHA1&digits=8&period=30`
+      : template.pos_algorithm === 2
+        ? `otpauth://totp/${issuer}:${templateId}?secret=${keySlice}...&issuer=${issuer}&algorithm=SHA1&digits=8&period=30`
+        : undefined;
   return (
     <div>
       {oauthUri && (